[dat]
AND1 had only one entry for baiard, corresponding to the first two baiard entries here (which were also conflated in the print and online editions of AND2 until the present revision in November 2013). On the whole, it seems to make sense to separate into two entries baiard “bay, dappled horse” (adj. and subst.) < badius (baiard1) and the proper name Baiard (Baiard2), the mythological horse of Les Quatre Fils Aymon which acquired a certain notoriety in both French and English. On this, see especially W. Rothwell, “Anglo-French and English society in Chaucer’s The Reeve’s Tale”, English Studies, 87:5 (2006), 511-538 (pp. 511-514). To this may be added the isolated examples of Bayard in English place-names: see David Parsons, Tania Styles, Carole Hough, The Vocabulary of English Place-Names (Nottingham, Centre for English Name Studies, 1997), 38: Bayard’s Green (field-name), 1194 Northamptonshire; Bayardacher (field-name), 1361 West Yorkshire; Bayard’s Cove, 1351 Devonshire. A parallel is the way in which Renart (originally the eponymous protagonist of the O.F. Roman de Renart) became the normal word for “fox” in French (replacing goupil < vulpĕcŭla); reflexes of renart survive in dialectal English (Survey of English Dialects IV.5.11).
AND2 added baiardour, with a gloss which has now been modified; implicit in baiardour is the simplex baiard, widely attested in continental French (Gdf and DMF), and found in both English and (especially) Latin. The OED only has baiard from 1642, and the MED citations could be construed as being Latin, not Middle English; as, indeed, could those here in baiard3. AND2’s baiart1 is the same word with a slightly extended sense (the semantic extension will be obvious enough to anyone who has ever slept on an old-fashioned camp bed) and two of DMLBS’s apparently Latin attestations could be Anglo-Norman, and so are included here.
Baiard3 is of uncertain origin (TLF sub bard). The FEW proposes bajulus, rejected by TLF on phonetic grounds (no early forms have -ill-); implicitly by OED sub baiardour (“Erroneously connected in the Dictionaries with Latin bājulātor”), and by REW (888 in fine); MED suggests it is “prob. a special use of baiard (1)”, “bay horse”, a position adopted also by G. Rohlfs (cf. Corominas, DCECL 1,430b). This is semantically explicable (cf. English clothes-horse, saw-horse; French chevalet; Italian cavaletto).
The cognate words in other Romance languages are probably French borrowings: Occitan (baiart), Catalan (baiard: Alcover/Moll, DCBV 2,212a), Castilian (baiardo: Corominas, DCECL 1,430b) and Italian (baiardo: DEI 1,408a).