diff --git a/TODO.md b/TODO.md
index 2d6fe3d..2a642b8 100644
--- a/TODO.md
+++ b/TODO.md
@@ -34,10 +34,17 @@ across every hour and content type in this app.
    date/entry already resolves correctly end-to-end); what's left is authoring/importing more
    content in that same shape across the rest of the calendar:
    - Latin saint/octave/named-feast names for the bilingual date/day-label header (see
-     "Bilingual, merged date/day-label header" below) — the `{en, la}` mechanism is built and
-     every proper name falls back to English gracefully, but zero saints, octaves, or named
-     temporal feasts have an authored Latin name anywhere in `src/data/**`. Weekday names,
-     month names, rank labels, and season/ordinal phrasing already have real Latin.
+     "Bilingual, merged date/day-label header" below and the dated log's new entry at the
+     bottom of this file) — `SanctoralIdentity`/`SaintRecord`/`TemporalFeastRecord`/
+     `ActiveOctave` now carry a real optional `nameLa` field, threaded end-to-end through
+     `calendar/day-label.ts`'s `biName` helper (live-verified: winner, octave-headline, and
+     commemoration branches all render authored Latin, not the English fallback, for a proof
+     set of 12 records — all 11 named temporal feasts plus St. Lawrence). Zero saints besides
+     St. Lawrence have an authored `nameLa` yet — this is now real bulk-content work in an
+     already-proven shape, same "one saint at a time, sourced against the reference engine's
+     own `[Officium]`/`[Rank]` title, nominative-noun-phrase form" methodology used for the
+     named temporal feasts. Weekday names, month names, rank labels, and season/ordinal
+     phrasing already had real Latin before this.
    - Matins sanctoral-side readings: the per-book Matins responsory pool has only one book
      seeded (`isa`) — needs expanding. Bible-plan TSV content also isn't yet in a test table
      (see "Bible-plan TSV — bulk conversion done" below).
@@ -4383,3 +4390,42 @@ not just under this app's implementation of them.
 Neither is "unauthored content pending" — there is no historical text for either case to author.
 Dropped from the "Open work" list entirely rather than marked done-with-a-caveat, since authoring
 something anyway would mean inventing text that never existed.
+
+### Bilingual header `nameLa` mechanism (2026-08-31)
+
+Picked up the standing "Latin saint/octave/named-feast names" backlog item. The `Bi`
+(`{en, la}`) *display* wrapper already existed in `calendar/day-label.ts`, but the underlying
+*data* had no bilingual name field at all — `SaintRecord.name`, `TemporalFeastRecord.name`, and
+the derived `SanctoralIdentity`/`ActiveOctave`/`Commemoration` types were plain English strings,
+so every proper name necessarily fell back through `biFallback`.
+
+Added an optional `nameLa?: string` alongside `name` on `SanctoralIdentity` (`calendar/types.ts`),
+`SaintRecord`/`SanctoralCandidate` (`calendar/feasts.ts`), `TemporalFeastRecord`
+(`calendar/temporal-feasts.ts`), and `ActiveOctave` (`calendar/octaves.ts`), then threaded it
+through every construction site that had been spreading `id`/`name`/`rank` (`collision.ts`,
+`commemorations.ts`, `movable-feasts.ts`, `index.ts` x3, `vespers.ts` x2,
+`octaves.ts`'s `considerCandidate`). `day-label.ts`'s old `biFallback(name)` calls became
+`biName(name, nameLa)`, which still falls back to the English string when `nameLa` is absent —
+the "surface real text, don't block on missing" convention preserved exactly, just now backed by
+a real field instead of no field at all.
+
+Authored `nameLa` for all 11 named temporal feasts as the proof set (each sourced from the
+reference engine's own `[Officium]`/`[Rank]` title, adapted from the source's genitive/ablative
+liturgical-title style to this app's nominative-noun-phrase naming convention — e.g. "In
+Ascensione Domini" → `Ascensio Domini`, "Sacratissimi Cordis Domini Nostri Jesu Christi" →
+`Sacratissimum Cor Domini Nostri Jesu Christi`) plus St. Lawrence as the one saint, chosen
+specifically to exercise the octave-headline (`octaveCoreName`) and octave-commemoration code
+paths, not just the plain-winner path the temporal feasts alone would have covered. Live-verified
+end-to-end via a throwaway scratch test (removed after confirming) that Pentecost's/the
+Ascension's/the Immaculate Heart's own winner label, St. Lawrence's mid-octave and closing-day
+octave label, and his octave *commemoration* line (Aug 12) all render the authored Latin, not the
+English fallback. Six pre-existing `toEqual` test fixtures across `august-sanctoral.test.ts`,
+`octaves.test.ts`, `transfer.test.ts`, and `december-sanctoral.test.ts` needed their expected
+objects updated to include the new `nameLa` key (Christmas's own octave-commemoration entries too,
+since `christmas-day.yml` picked up a name in this same pass). `npm test` (807 passed) and
+`tsc --noEmit` pass.
+
+**Not started**: `nameLa` for the other ~220 saints — the mechanism is now proven in all three
+code paths (plain winner, octave headline, sanctoral commemoration); what's left is the same
+per-saint sourcing pass the sanctoral-content sweep itself used, just for a name instead of a
+collect.
diff --git a/src/calendar/collision.ts b/src/calendar/collision.ts
index 3632ac1..f030cc0 100644
--- a/src/calendar/collision.ts
+++ b/src/calendar/collision.ts
@@ -19,11 +19,11 @@ export interface CollisionResult {
 }
 
 function asWinner(candidate: SanctoralIdentity): DayWinner {
-  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, rank: candidate.rank };
+  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, nameLa: candidate.nameLa, rank: candidate.rank };
 }
 
 function asCommemoration(candidate: SanctoralIdentity): Commemoration {
-  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, rank: candidate.rank };
+  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, nameLa: candidate.nameLa, rank: candidate.rank };
 }
 
 /**
diff --git a/src/calendar/commemorations.ts b/src/calendar/commemorations.ts
index 4a2745a..56a312f 100644
--- a/src/calendar/commemorations.ts
+++ b/src/calendar/commemorations.ts
@@ -83,11 +83,11 @@ export interface OccurrenceResult {
 }
 
 function sanctoralCommemoration(candidate: SanctoralIdentity): Commemoration {
-  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, rank: candidate.rank };
+  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, nameLa: candidate.nameLa, rank: candidate.rank };
 }
 
 function sanctoralWinner(candidate: SanctoralIdentity): DayWinner {
-  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, rank: candidate.rank };
+  return { kind: 'sanctoral', id: candidate.id, name: candidate.name, nameLa: candidate.nameLa, rank: candidate.rank };
 }
 
 /**
diff --git a/src/calendar/day-label.ts b/src/calendar/day-label.ts
index 458c68b..b9c97ca 100644
--- a/src/calendar/day-label.ts
+++ b/src/calendar/day-label.ts
@@ -12,12 +12,14 @@
 //
 // Bilingual: every label is built as a `Bi` (`{en, la}`) pair throughout.
 // Proper names (a saint's name, an octave's name, a named temporal feast's
-// name) have no authored Latin form anywhere in `data/` today — those use
-// the English string as their own `la` value too (same "surface real text
-// rather than block on missing" convention used elsewhere in this app),
-// rather than leaving Latin mode showing blanks. Only the closed,
+// name) carry an optional `nameLa` field alongside the required English
+// `name` — see calendar/types.ts's `SanctoralIdentity.nameLa` doc comment.
+// Most saints still have no authored Latin name; `biName` falls back to
+// the English string as the `la` value in that case (same "surface real
+// text rather than block on missing" convention used elsewhere in this
+// app), rather than leaving Latin mode showing blanks. The closed,
 // mechanism-level vocabulary here (weekdays, ranks, season/ordinal
-// phrasing) has real Latin authored.
+// phrasing) has always had real Latin authored, independent of this.
 import type { FeastClass, LiturgicalDay, TemporalCategory, Weekday } from './types';
 import { easterSunday } from './easter';
 import { adventStart, firstSundayStrictlyAfter, sundayOnOrBefore } from './temporal';
@@ -36,10 +38,11 @@ function bi(en: string, la: string): Bi {
   return { en, la };
 }
 
-/** A proper name with no authored Latin form yet — the English string
- * stands in for `la` too. See file-header note. */
-function biFallback(name: string): Bi {
-  return { en: name, la: name };
+/** A proper name (saint, octave, named temporal feast) with an optional
+ * authored Latin form — falls back to the English string when `nameLa`
+ * hasn't been authored yet, same convention as `biFallback` above. */
+function biName(name: string, nameLa: string | undefined): Bi {
+  return { en: name, la: nameLa ?? name };
 }
 
 function joinBi(items: Bi[], sep = ' — '): Bi {
@@ -348,13 +351,13 @@ function temporalLabel(day: LiturgicalDay): Bi {
  * own winner is the feast itself, handled above before this is ever
  * called) — kept simple rather than special-cased for that rare edge case
  * (see applyOctaves's own `isOwnStartDay` comment in calendar/index.ts for
- * when it can happen). The octave's own `name` has no authored Latin form
- * (see file header), so both languages currently show the same name text
- * — only the surrounding phrasing differs. */
+ * when it can happen). Falls back to the English name for `la` too when
+ * the octave's own record has no authored `nameLa` yet (see file header). */
 function octaveCoreName(octave: ActiveOctave): Bi {
+  const name = biName(octave.name, octave.nameLa);
   return octave.isClosingDay
-    ? bi(`Octave of ${octave.name}`, `In Octava ${octave.name}`)
-    : bi(`${ordinal(octave.dayNumber)} Day within the Octave of ${octave.name}`, `${ordinalLa(octave.dayNumber)} die infra Octavam ${octave.name}`);
+    ? bi(`Octave of ${name.en}`, `In Octava ${name.la}`)
+    : bi(`${ordinal(octave.dayNumber)} Day within the Octave of ${name.en}`, `${ordinalLa(octave.dayNumber)} die infra Octavam ${name.la}`);
 }
 
 function octaveLabel(octave: ActiveOctave): Bi {
@@ -405,8 +408,8 @@ const CROSS_DAY_VESPERS_LABELS: Record<'today' | 'tomorrow', Bi> = {
  * - `sanctoral`: every commemorated saint, plain name, no rank (multiple
  *   real ones can coexist — e.g. two colliding saints on the same date —
  *   this app's own "generous commemorations" design keeps every one of
- *   them, not just the first). No authored Latin saint names exist yet
- *   (see file header), so `la` falls back to the same English name.
+ *   them, not just the first). `la` uses the saint's own `nameLa` when
+ *   authored, else falls back to the same English name (see file header).
  * - `temporal`: the day's own real Sunday/feria identity, if
  *   `decideOccurrence` demoted it to a commemoration (`ordinary-sunday`/
  *   `privileged-feria`/`privileged-feria-minor`) — matched by id against
@@ -438,7 +441,7 @@ function collectCommemorations(
   const octaves: Bi[] = [];
   for (const c of day.commemorations) {
     if (c.kind === 'sanctoral') {
-      const name = biFallback(c.name);
+      const name = biName(c.name, c.nameLa);
       sanctoral.push(
         c.vespersNote
           ? bi(`${name.en} (${CROSS_DAY_VESPERS_LABELS[c.vespersNote].en})`, `${name.la} (${CROSS_DAY_VESPERS_LABELS[c.vespersNote].la})`)
@@ -450,7 +453,7 @@ function collectCommemorations(
       }
     } else if (opts.showOctaves && c.id !== opts.excludeOctaveId) {
       const octave = activeOctaves.find((a) => a.id === c.id);
-      octaves.push(octave ? octaveCommemorationLabel(octave) : biFallback(c.name));
+      octaves.push(octave ? octaveCommemorationLabel(octave) : biName(c.name, c.nameLa));
     }
   }
   return { sanctoral, temporal, octaves };
@@ -542,7 +545,7 @@ export function getDayLabel(day: LiturgicalDay): Partial<Record<string, string>>
       showOctaves: day.temporalCategory === 'ordinary-feria',
     });
     const rank = formatRank(day.winner.rank);
-    const winnerName = biFallback(day.winner.name);
+    const winnerName = biName(day.winner.name, day.winner.nameLa);
     const winner = bi(`${winnerName.en} (${rank.en})`, `${winnerName.la} (${rank.la})`);
     return joinBi([winner, ...temporal, ...sanctoral, ...octaves]);
   }
@@ -554,7 +557,7 @@ export function getDayLabel(day: LiturgicalDay): Partial<Record<string, string>>
   // temporal-feasts.ts) and fall through further down.
   const namedFeast = getTemporalFeastRecord(day.winner.id);
   if (namedFeast) {
-    const name = biFallback(namedFeast.name);
+    const name = biName(namedFeast.name, namedFeast.nameLa);
     const primary = namedFeast.rank
       ? bi(`${name.en} (${formatRank(namedFeast.rank).en})`, `${name.la} (${formatRank(namedFeast.rank).la})`)
       : name;
diff --git a/src/calendar/feasts.ts b/src/calendar/feasts.ts
index 0fbe593..6f611a6 100644
--- a/src/calendar/feasts.ts
+++ b/src/calendar/feasts.ts
@@ -15,6 +15,9 @@ import sanctoralCalendarData from '../data/calendar/sanctoral-calendar.yml';
 export interface SaintRecord {
   id: string;
   name: string;
+  /** Latin form of `name`, when authored — see calendar/types.ts's
+   * `SanctoralIdentity.nameLa` doc comment for the display fallback. */
+  nameLa?: string;
   rank: FeastClass;
   common: string;
   propers: string | null;
@@ -138,6 +141,7 @@ for (const mod of Object.values(saintModules)) {
 export interface SanctoralCandidate {
   id: string;
   name: string;
+  nameLa?: string;
   rank: FeastClass;
 }
 
@@ -157,6 +161,6 @@ export function getSanctoralCandidatesFor(isoDate: string): SanctoralCandidate[]
     if (!saint) {
       throw new Error(`sanctoral-calendar.yml references unknown saint id '${id}'`);
     }
-    return { id: saint.id, name: saint.name, rank: saint.rank };
+    return { id: saint.id, name: saint.name, nameLa: saint.nameLa, rank: saint.rank };
   });
 }
diff --git a/src/calendar/index.ts b/src/calendar/index.ts
index ac6b3e4..058579e 100644
--- a/src/calendar/index.ts
+++ b/src/calendar/index.ts
@@ -237,7 +237,7 @@ function applyChristmasOctaveSunday(
       if (idx !== -1) {
         commemorations.splice(idx, 1);
       }
-      return { kind: 'sanctoral', id: displaced.id, name: displaced.name, rank: displaced.rank };
+      return { kind: 'sanctoral', id: displaced.id, name: displaced.name, nameLa: displaced.nameLa, rank: displaced.rank };
     }
   }
 
@@ -290,7 +290,7 @@ function applyMarianSaturday(
   if (winner.rank !== 'simplex') {
     return winner;
   }
-  commemorations.push({ kind: 'sanctoral', id: winner.id, name: winner.name, rank: winner.rank });
+  commemorations.push({ kind: 'sanctoral', id: winner.id, name: winner.name, nameLa: winner.nameLa, rank: winner.rank });
   return MARIAN_SATURDAY;
 }
 
@@ -343,7 +343,7 @@ function applyOctaves(isoDate: string, winner: DayWinner, commemorations: Commem
     if (cmp < 0 || tiedAgainstClosingDay) {
       const isOneOfTheseOctaves = octaves.some((o) => o.id === winner.id);
       if (!isOneOfTheseOctaves) {
-        commemorations.push({ kind: 'sanctoral', id: winner.id, name: winner.name, rank: winner.rank });
+        commemorations.push({ kind: 'sanctoral', id: winner.id, name: winner.name, nameLa: winner.nameLa, rank: winner.rank });
         resolvedWinner = { kind: 'temporal', id: resolveTemporalId(isoDate) };
       }
     }
@@ -356,7 +356,7 @@ function applyOctaves(isoDate: string, winner: DayWinner, commemorations: Commem
     // again alongside itself would be redundant.
     const isOwnStartDay = octave.dayNumber === 1 && resolvedWinner.kind === 'temporal';
     if (!isSelf && !isOwnStartDay) {
-      commemorations.push({ kind: 'octave', id: octave.id, name: octave.name });
+      commemorations.push({ kind: 'octave', id: octave.id, name: octave.name, nameLa: octave.nameLa });
     }
   }
 
diff --git a/src/calendar/movable-feasts.ts b/src/calendar/movable-feasts.ts
index 96308df..4710471 100644
--- a/src/calendar/movable-feasts.ts
+++ b/src/calendar/movable-feasts.ts
@@ -83,7 +83,7 @@ export function applyMovableFeasts(isoDate: string, winner: DayWinner, commemora
       if (resolvedWinner.kind === 'temporal') {
         commemorations.push({ kind: 'temporal', id: resolvedWinner.id });
       } else {
-        commemorations.push({ kind: 'sanctoral', id: resolvedWinner.id, name: resolvedWinner.name, rank: resolvedWinner.rank });
+        commemorations.push({ kind: 'sanctoral', id: resolvedWinner.id, name: resolvedWinner.name, nameLa: resolvedWinner.nameLa, rank: resolvedWinner.rank });
       }
       resolvedWinner = FEAST_WINNER;
       continue;
@@ -95,7 +95,7 @@ export function applyMovableFeasts(isoDate: string, winner: DayWinner, commemora
     } else if (compareFeastClass(resolvedWinner.rank, rank) >= 0) {
       commemorations.push({ kind: 'temporal', id: feast.id });
     } else {
-      commemorations.push({ kind: 'sanctoral', id: resolvedWinner.id, name: resolvedWinner.name, rank: resolvedWinner.rank });
+      commemorations.push({ kind: 'sanctoral', id: resolvedWinner.id, name: resolvedWinner.name, nameLa: resolvedWinner.nameLa, rank: resolvedWinner.rank });
       resolvedWinner = FEAST_WINNER;
     }
   }
diff --git a/src/calendar/octaves.ts b/src/calendar/octaves.ts
index 133360b..80ad38b 100644
--- a/src/calendar/octaves.ts
+++ b/src/calendar/octaves.ts
@@ -17,6 +17,9 @@ import { compareFeastClass, minimumOutrightWinningRank } from './commemorations'
 export interface ActiveOctave {
   id: string;
   name: string;
+  /** Latin form of `name`, when authored — see calendar/types.ts's
+   * `SanctoralIdentity.nameLa` doc comment for the display fallback. */
+  nameLa?: string;
   /** This octave's own effective rank *today* — the ordinary `wins`
    * threshold on every day except its own closing day, where it's
    * `closingDayRank` instead (see calendar/types.ts's OctaveConfig).
@@ -49,6 +52,7 @@ function considerCandidate(
   startDate: string,
   id: string,
   name: string,
+  nameLa: string | undefined,
   octave: OctaveConfig | undefined,
 ): void {
   if (!octave?.enabled || seen.has(id)) {
@@ -63,7 +67,7 @@ function considerCandidate(
   const dayNumber = offset + 1;
   const isClosingDay = dayNumber === days;
   const wins = isClosingDay ? (octave.closingDayRank ?? DEFAULT_CLOSING_DAY_RANK) : (octave.wins ?? DEFAULT_WINS);
-  active.push({ id, name, wins, dayNumber, isClosingDay });
+  active.push({ id, name, nameLa, wins, dayNumber, isClosingDay });
 }
 
 /** Every octave (sanctoral or temporal) whose window covers `isoDate`,
@@ -80,14 +84,14 @@ export function activeOctavesFor(isoDate: string): ActiveOctave[] {
     for (const candidate of getSanctoralCandidatesFor(candidateDate)) {
       const record = getSaintRecord(candidate.id);
       if (record) {
-        considerCandidate(active, seen, isoDate, candidateDate, record.id, record.name, record.octave);
+        considerCandidate(active, seen, isoDate, candidateDate, record.id, record.name, record.nameLa, record.octave);
       }
     }
 
     for (const feastId of temporalFeastIdsStartingOn(candidateDate)) {
       const record = getTemporalFeastRecord(feastId);
       if (record) {
-        considerCandidate(active, seen, isoDate, candidateDate, record.id, record.name, record.octave);
+        considerCandidate(active, seen, isoDate, candidateDate, record.id, record.name, record.nameLa, record.octave);
       }
     }
   }
diff --git a/src/calendar/temporal-feasts.ts b/src/calendar/temporal-feasts.ts
index 11ce5cf..155bfb5 100644
--- a/src/calendar/temporal-feasts.ts
+++ b/src/calendar/temporal-feasts.ts
@@ -30,6 +30,9 @@ export type MovableAnchor =
 export interface TemporalFeastRecord {
   id: string;
   name: string;
+  /** Latin form of `name`, when authored — see calendar/types.ts's
+   * `SanctoralIdentity.nameLa` doc comment for the display fallback. */
+  nameLa?: string;
   octave?: OctaveConfig;
   rank?: FeastClass;
   anchor?: MovableAnchor;
diff --git a/src/calendar/types.ts b/src/calendar/types.ts
index d5b948e..6156c31 100644
--- a/src/calendar/types.ts
+++ b/src/calendar/types.ts
@@ -103,6 +103,11 @@ export type TemporalCategory =
 export interface SanctoralIdentity {
   id: string;
   name: string;
+  /** Latin form of `name`, when authored (see `data/calendar/saints/*.yml`'s
+   * own `nameLa` field). Absent for the majority of saints still — display
+   * code falls back to `name` itself when this is missing, same "surface
+   * real text rather than block on missing" convention used elsewhere. */
+  nameLa?: string;
   rank: FeastClass;
 }
 
@@ -180,7 +185,7 @@ export type Commemoration =
       // carries no such qualifier.
       vespersNote?: 'today' | 'tomorrow';
     } & SanctoralIdentity)
-  | { kind: 'octave'; id: string; name: string };
+  | { kind: 'octave'; id: string; name: string; nameLa?: string };
 
 export interface LiturgicalDay {
   /** ISO date, e.g. "2026-08-09" */
diff --git a/src/calendar/vespers.ts b/src/calendar/vespers.ts
index cfe5d10..fe5f261 100644
--- a/src/calendar/vespers.ts
+++ b/src/calendar/vespers.ts
@@ -85,7 +85,7 @@ function commemorationOfDisplacedPredecessor(loser: DayWinner): Commemoration |
   if (loser.kind !== 'sanctoral' || loser.rank === 'simplex') {
     return undefined;
   }
-  return { kind: 'sanctoral', id: loser.id, name: loser.name, rank: loser.rank, vespersNote: 'today' };
+  return { kind: 'sanctoral', id: loser.id, name: loser.name, nameLa: loser.nameLa, rank: loser.rank, vespersNote: 'today' };
 }
 
 /**
@@ -120,7 +120,7 @@ function commemorationOfDisplacedSuccessor(winner: DayWinner, loser: DayWinner):
   if (forbids) {
     return undefined;
   }
-  return { kind: 'sanctoral', id: loser.id, name: loser.name, rank: loser.rank, vespersNote: 'tomorrow' };
+  return { kind: 'sanctoral', id: loser.id, name: loser.name, nameLa: loser.nameLa, rank: loser.rank, vespersNote: 'tomorrow' };
 }
 
 function tagVespersFrom(tomorrow: LiturgicalDay): LiturgicalDay {
diff --git a/src/data/calendar/saints/st-lawrence.yml b/src/data/calendar/saints/st-lawrence.yml
index 6a49d4a..bebfd41 100644
--- a/src/data/calendar/saints/st-lawrence.yml
+++ b/src/data/calendar/saints/st-lawrence.yml
@@ -6,6 +6,10 @@
 # antiphon.
 id: st-lawrence
 name: "St. Lawrence, Martyr"
+# Standard Latin form, matching this app's own "St. X, Rank" naming
+# convention (the source's own martyrology/kalendar entries for him use
+# the genitive "S. Laurentii Martyris", dependent on an implied "Festum").
+nameLa: "Sanctus Laurentius, Martyr"
 rank: duplex-2-classis
 common: common-of-a-martyr
 propers: "st-lawrence"
diff --git a/src/data/calendar/temporal-feasts/ascension.yml b/src/data/calendar/temporal-feasts/ascension.yml
index 50b67a1..6d082d7 100644
--- a/src/data/calendar/temporal-feasts/ascension.yml
+++ b/src/data/calendar/temporal-feasts/ascension.yml
@@ -15,6 +15,11 @@
 # — the `ordinary-feria` category was never actually load-bearing here.
 id: ascension
 name: "The Ascension of Our Lord"
+# Nominative form of the reference engine's own title ("In Ascensione
+# Domini", Pasc5-4.txt's [Officium]/[Rank] header), matching this app's
+# own nominative-noun-phrase naming convention rather than the source's
+# prepositional-phrase style.
+nameLa: "Ascensio Domini"
 rank: duplex-1-classis
 anchor:
   kind: easter
diff --git a/src/data/calendar/temporal-feasts/christ-the-king.yml b/src/data/calendar/temporal-feasts/christ-the-king.yml
index ecb8329..28a1a55 100644
--- a/src/data/calendar/temporal-feasts/christ-the-king.yml
+++ b/src/data/calendar/temporal-feasts/christ-the-king.yml
@@ -8,6 +8,11 @@
 # movable feast. See calendar/movable-feasts.ts for the occurrence rule.
 id: christ-the-king
 name: "Christ the King"
+# The feast's own traditional short Latin title (Pius XI's "Quas Primas"),
+# matching this app's nominative-noun-phrase naming convention — the
+# reference engine's own [Rank] title is genitive ("Domini Nostri Jesu
+# Christi Regis", Sancti/10-DU.txt), dependent on an implied "Festum".
+nameLa: "Christus Rex"
 rank: duplex-1-classis
 anchor:
   kind: nth-sunday-of-month
diff --git a/src/data/calendar/temporal-feasts/christmas-day.yml b/src/data/calendar/temporal-feasts/christmas-day.yml
index 378e293..fb29960 100644
--- a/src/data/calendar/temporal-feasts/christmas-day.yml
+++ b/src/data/calendar/temporal-feasts/christmas-day.yml
@@ -12,6 +12,10 @@
 # specifically.
 id: christmas-day
 name: "Christmas"
+# Nominative form of the reference engine's own title ("In Nativitate
+# Domini", Sancti/12-25.txt's [Rank]), matching this app's own
+# nominative-noun-phrase naming convention.
+nameLa: "Nativitas Domini"
 rank: duplex-1-classis
 octave:
   enabled: true
diff --git a/src/data/calendar/temporal-feasts/circumcision.yml b/src/data/calendar/temporal-feasts/circumcision.yml
index 3db8442..afa2c43 100644
--- a/src/data/calendar/temporal-feasts/circumcision.yml
+++ b/src/data/calendar/temporal-feasts/circumcision.yml
@@ -20,6 +20,10 @@
 # not winner resolution at all.
 id: circumcision
 name: "The Circumcision of Our Lord"
+# Nominative form of the reference engine's own title ("In Circumcisione
+# Domini", Sancti/01-01.txt's [Rank]), matching this app's own
+# nominative-noun-phrase naming convention.
+nameLa: "Circumcisio Domini"
 rank: duplex-2-classis
 anchor:
   kind: fixed-date
diff --git a/src/data/calendar/temporal-feasts/corpus-christi.yml b/src/data/calendar/temporal-feasts/corpus-christi.yml
index a3a7f33..0e297b7 100644
--- a/src/data/calendar/temporal-feasts/corpus-christi.yml
+++ b/src/data/calendar/temporal-feasts/corpus-christi.yml
@@ -14,6 +14,11 @@
 # day's real winner.
 id: corpus-christi
 name: "The Most Holy Body of Christ"
+# Common short Latin title, well attested in the reference engine's own
+# text ("Festum Sanctissimi Corporis Christi", Tempora/Pent01-4.txt's
+# [Officium]) — already a nominative noun phrase on its own, no
+# adaptation needed.
+nameLa: "Corpus Christi"
 rank: duplex-1-classis
 anchor:
   kind: easter
diff --git a/src/data/calendar/temporal-feasts/holy-name-of-jesus.yml b/src/data/calendar/temporal-feasts/holy-name-of-jesus.yml
index d437016..616ba55 100644
--- a/src/data/calendar/temporal-feasts/holy-name-of-jesus.yml
+++ b/src/data/calendar/temporal-feasts/holy-name-of-jesus.yml
@@ -16,6 +16,10 @@
 # the day.
 id: holy-name-of-jesus
 name: "The Most Holy Name of Jesus"
+# Nominative form of the reference engine's own title ("Sanctissimi
+# Nominis Jesu", Sancti/01-00.txt's [Rank]), matching this app's own
+# nominative-noun-phrase naming convention.
+nameLa: "Sanctissimum Nomen Jesu"
 rank: duplex-2-classis
 anchor:
   kind: fixed-date
diff --git a/src/data/calendar/temporal-feasts/immaculate-heart-of-mary.yml b/src/data/calendar/temporal-feasts/immaculate-heart-of-mary.yml
index 570f2f7..dde1dbb 100644
--- a/src/data/calendar/temporal-feasts/immaculate-heart-of-mary.yml
+++ b/src/data/calendar/temporal-feasts/immaculate-heart-of-mary.yml
@@ -11,6 +11,10 @@
 # own content.
 id: immaculate-heart-of-mary
 name: "The Immaculate Heart of the Blessed Virgin Mary"
+# Nominative form of the reference engine's own title ("Immaculati Cordis
+# Beatæ Mariæ Virginis", Sancti/08-22.txt's [Rank]), matching this app's
+# own nominative-noun-phrase naming convention.
+nameLa: "Immaculatum Cor Beatæ Mariæ Virginis"
 rank: duplex-2-classis
 anchor:
   kind: easter
diff --git a/src/data/calendar/temporal-feasts/marian-saturday.yml b/src/data/calendar/temporal-feasts/marian-saturday.yml
index 452e161..a256c67 100644
--- a/src/data/calendar/temporal-feasts/marian-saturday.yml
+++ b/src/data/calendar/temporal-feasts/marian-saturday.yml
@@ -5,4 +5,9 @@
 # for how a day actually becomes this.
 id: marian-saturday
 name: "Our Lady's Saturday"
+# Adapted to a nominative noun phrase from the reference engine's own
+# title ("Sanctæ Mariæ Sabbato", Commune/C10.txt's [Officium] — an
+# ablative time-when construction, "on the Saturday of Holy Mary"),
+# matching this app's own nominative naming convention.
+nameLa: "Sabbatum Sanctæ Mariæ"
 rank: simplex
diff --git a/src/data/calendar/temporal-feasts/patronage-of-st-joseph.yml b/src/data/calendar/temporal-feasts/patronage-of-st-joseph.yml
index 9471c69..1c15126 100644
--- a/src/data/calendar/temporal-feasts/patronage-of-st-joseph.yml
+++ b/src/data/calendar/temporal-feasts/patronage-of-st-joseph.yml
@@ -21,6 +21,11 @@
 # (PascN-D = Easter + 7N + D, e.g. Ascension = Pasc5-4 = Easter+39).
 id: patronage-of-st-joseph
 name: "The Patronage of St. Joseph"
+# Nominative form of the reference engine's own title ("In Octava
+# Patrocinii S. Joseph", Tempora/Pasc3-3.txt's [Officium], octave-day
+# form of the feast's own genitive "Patrocinii S. Joseph"), matching this
+# app's own nominative-noun-phrase naming convention.
+nameLa: "Patrocinium Sancti Joseph"
 rank: duplex-1-classis
 anchor:
   kind: easter
diff --git a/src/data/calendar/temporal-feasts/pentecost-sunday.yml b/src/data/calendar/temporal-feasts/pentecost-sunday.yml
index 62dc34c..b1966ee 100644
--- a/src/data/calendar/temporal-feasts/pentecost-sunday.yml
+++ b/src/data/calendar/temporal-feasts/pentecost-sunday.yml
@@ -10,6 +10,9 @@
 # before it gets the chance.
 id: pentecost-sunday
 name: "Pentecost"
+# Reference engine's own [Officium] title, Tempora/Pent00-0.txt — already
+# a nominative noun phrase, no adaptation needed.
+nameLa: "Dominica Pentecostes"
 rank: duplex-1-classis
 octave:
   enabled: true
diff --git a/src/data/calendar/temporal-feasts/sacred-heart.yml b/src/data/calendar/temporal-feasts/sacred-heart.yml
index 41711dc..e6f122d 100644
--- a/src/data/calendar/temporal-feasts/sacred-heart.yml
+++ b/src/data/calendar/temporal-feasts/sacred-heart.yml
@@ -10,6 +10,10 @@
 # temporal-feasts.ts's own doc comment) a record to live on.
 id: sacred-heart
 name: "The Most Sacred Heart of Our Lord Jesus Christ"
+# Nominative form of the reference engine's own title ("Sacratissimi
+# Cordis Domini Nostri Jesu Christi", Tempora/Pent02-5.txt's [Officium]),
+# matching this app's own nominative-noun-phrase naming convention.
+nameLa: "Sacratissimum Cor Domini Nostri Jesu Christi"
 rank: duplex-1-classis
 anchor:
   kind: easter
diff --git a/tests/calendar/august-sanctoral.test.ts b/tests/calendar/august-sanctoral.test.ts
index 24452e7..6fc517e 100644
--- a/tests/calendar/august-sanctoral.test.ts
+++ b/tests/calendar/august-sanctoral.test.ts
@@ -71,6 +71,7 @@ describe('August sanctoral pull (first pass)', () => {
       kind: 'sanctoral',
       id: 'st-lawrence',
       name: 'St. Lawrence, Martyr',
+      nameLa: 'Sanctus Laurentius, Martyr',
       rank: 'duplex-2-classis',
     });
     expect(getDayCollect(day).status.en).toBe('verified');
@@ -86,7 +87,7 @@ describe('August sanctoral pull (first pass)', () => {
     expect(clareDay.winner.kind).toBe('temporal');
     expect(clareDay.commemorations).toEqual([
       { kind: 'sanctoral', id: 'st-clare', name: 'St. Clare, Virgin', rank: 'simplex' },
-      { kind: 'octave', id: 'st-lawrence', name: 'St. Lawrence, Martyr' },
+      { kind: 'octave', id: 'st-lawrence', name: 'St. Lawrence, Martyr', nameLa: 'Sanctus Laurentius, Martyr' },
     ]);
     // Aug 22 is the Assumption's own octave day (In Octava Assumptionis),
     // Duplex, blocking Ss. Timothy/Hippolytus/Symphorian the same way --
diff --git a/tests/calendar/december-sanctoral.test.ts b/tests/calendar/december-sanctoral.test.ts
index 89fa9f0..fb9dc3a 100644
--- a/tests/calendar/december-sanctoral.test.ts
+++ b/tests/calendar/december-sanctoral.test.ts
@@ -84,7 +84,7 @@ describe('December sanctoral pull (first pass, 12/12)', () => {
     // dedicated stacking test below for the full week's build-up.
     expect(stephen.commemorations).toEqual([
       { kind: 'temporal', id: expect.any(String) },
-      { kind: 'octave', id: 'christmas-day', name: 'Christmas' },
+      { kind: 'octave', id: 'christmas-day', name: 'Christmas', nameLa: 'Nativitas Domini' },
     ]);
   });
 
@@ -101,7 +101,7 @@ describe('December sanctoral pull (first pass, 12/12)', () => {
     // all stacked up and commemorate alongside him.
     expect(day.commemorations).toEqual([
       { kind: 'temporal', id: expect.any(String) },
-      { kind: 'octave', id: 'christmas-day', name: 'Christmas' },
+      { kind: 'octave', id: 'christmas-day', name: 'Christmas', nameLa: 'Nativitas Domini' },
       { kind: 'octave', id: 'st-stephen-protomartyr', name: 'St. Stephen, Protomartyr' },
       { kind: 'octave', id: 'st-john-apostle', name: 'St. John, Apostle and Evangelist' },
       { kind: 'octave', id: 'holy-innocents', name: 'The Holy Innocents, Martyrs' },
@@ -155,7 +155,7 @@ describe('December sanctoral pull (first pass, 12/12)', () => {
     const dec30 = resolveDay('2033-12-30'); // no saint of its own -- a plain Octave-of-the-Nativity day
     expect(dec30.winner.kind).toBe('temporal');
     expect(dec30.commemorations).toEqual([
-      { kind: 'octave', id: 'christmas-day', name: 'Christmas' },
+      { kind: 'octave', id: 'christmas-day', name: 'Christmas', nameLa: 'Nativitas Domini' },
       { kind: 'octave', id: 'st-stephen-protomartyr', name: 'St. Stephen, Protomartyr' },
       { kind: 'octave', id: 'st-john-apostle', name: 'St. John, Apostle and Evangelist' },
       { kind: 'octave', id: 'holy-innocents', name: 'The Holy Innocents, Martyrs' },
diff --git a/tests/calendar/octaves.test.ts b/tests/calendar/octaves.test.ts
index 495ddf6..cf1871d 100644
--- a/tests/calendar/octaves.test.ts
+++ b/tests/calendar/octaves.test.ts
@@ -10,7 +10,14 @@ describe('activeOctavesFor', () => {
   it("finds a saint's own octave on its own day (day 1) and through day 8, not on day 9", () => {
     const day1 = activeOctavesFor('2026-08-10'); // St. Lawrence's own day
     expect(day1).toEqual([
-      { id: 'st-lawrence', name: 'St. Lawrence, Martyr', wins: 'semiduplex', dayNumber: 1, isClosingDay: false },
+      {
+        id: 'st-lawrence',
+        name: 'St. Lawrence, Martyr',
+        nameLa: 'Sanctus Laurentius, Martyr',
+        wins: 'semiduplex',
+        dayNumber: 1,
+        isClosingDay: false,
+      },
     ]);
 
     // Aug 17 is also day 3 of the Assumption's own octave (started Aug 15) --
@@ -19,7 +26,14 @@ describe('activeOctavesFor', () => {
     // pattern, not a per-saint quirk (see calendar/types.ts's OctaveConfig).
     const day8 = activeOctavesFor('2026-08-17');
     expect(day8).toEqual([
-      { id: 'st-lawrence', name: 'St. Lawrence, Martyr', wins: 'duplex', dayNumber: 8, isClosingDay: true },
+      {
+        id: 'st-lawrence',
+        name: 'St. Lawrence, Martyr',
+        nameLa: 'Sanctus Laurentius, Martyr',
+        wins: 'duplex',
+        dayNumber: 8,
+        isClosingDay: true,
+      },
       {
         id: 'assumption',
         name: 'The Assumption of the Blessed Virgin Mary',
@@ -37,7 +51,14 @@ describe('activeOctavesFor', () => {
   it("Pentecost's octave uses its own configured threshold (duplex), not the default (semiduplex)", () => {
     const octaves = activeOctavesFor('2026-05-29'); // within Pentecost's octave, 2026
     expect(octaves).toEqual([
-      { id: 'pentecost-sunday', name: 'Pentecost', wins: 'duplex', dayNumber: 6, isClosingDay: false },
+      {
+        id: 'pentecost-sunday',
+        name: 'Pentecost',
+        nameLa: 'Dominica Pentecostes',
+        wins: 'duplex',
+        dayNumber: 6,
+        isClosingDay: false,
+      },
     ]);
     expect(strictestThreshold(octaves)).toBe('duplex');
   });
diff --git a/tests/calendar/transfer.test.ts b/tests/calendar/transfer.test.ts
index 86d7683..2575455 100644
--- a/tests/calendar/transfer.test.ts
+++ b/tests/calendar/transfer.test.ts
@@ -46,6 +46,7 @@ describe('transfer mechanism (resolveDay integration)', () => {
       kind: 'sanctoral',
       id: 'st-lawrence',
       name: 'St. Lawrence, Martyr',
+      nameLa: 'Sanctus Laurentius, Martyr',
       rank: 'duplex-2-classis',
     });
   });
@@ -74,7 +75,7 @@ describe('transfer mechanism (resolveDay integration)', () => {
     expect(saturday.winner).toEqual({ kind: 'temporal', id: 'pentecost-sunday' });
     expect(saturday.commemorations).toEqual([
       { kind: 'sanctoral', id: 'st-felix-i', name: 'St. Felix I, Pope and Martyr', rank: 'simplex' },
-      { kind: 'octave', id: 'pentecost-sunday', name: 'Pentecost' },
+      { kind: 'octave', id: 'pentecost-sunday', name: 'Pentecost', nameLa: 'Dominica Pentecostes' },
     ]);
 
     // Felix doesn't reach Trinity Sunday at all now. Trinity Sunday 2026
@@ -93,7 +94,7 @@ describe('transfer mechanism (resolveDay integration)', () => {
     });
     expect(sunday.commemorations).toEqual([
       { kind: 'temporal', id: 'post-pentecost-01' },
-      { kind: 'octave', id: 'pentecost-sunday', name: 'Pentecost' },
+      { kind: 'octave', id: 'pentecost-sunday', name: 'Pentecost', nameLa: 'Dominica Pentecostes' },
     ]);
   });
 });