feastyoudaoicibaDictYouDict[feast 词源字典]
feast: [13] The notion of ‘eating’ is a secondary semantic development for feast, whose underlying meaning (as may be guessed from the related festival [14] and festivity [14]) has more to do with joyousness than with the appeasement of hunger. Its ultimate source is the Latin adjective festus, which meant ‘joyful, merry’. This was used as a plural noun, festa, meaning ‘celebratory ceremonies, particularly of a religious nature’, which came down to Old French as feste.

This was the source of English feast, and its modern French descendant gave English fête [18]. Incidentally, the sense ‘sumptuous meal’, present in feast but not in fête, goes back to the Latin singular noun festum. Also related is festoon [17], acquired via French from Italian festone, which originally meant ‘ornament for a festive occasion’; and fair (as in fairground) comes ultimately from Latin fēria, first cousin to festus.
=> fair, festival, festoon, fête[feast etymology, feast origin, 英语词源]
feast (v.)youdaoicibaDictYouDict
c. 1300, "partake of a feast," from Old French fester "to feast, make merry; observe (a holiday)" (Modern French fêter), from feste "religious festival" (see feast (n.)). Related: Feasted; feasting.
feast (n.)youdaoicibaDictYouDict
c. 1200, "secular celebration with feasting and entertainment" (often held on a church holiday); c. 1300, "religious anniversary characterized by rejoicing" (rather than fasting), from Old French feste "religious festival, holy day; holiday; market, fair; noise, racket; jest, fun" (12c., Modern French fête), from Vulgar Latin *festa (fem. singular; also source of Italian festa, Spanish fiesta), from Latin festa "holidays, feasts, festal banquets," noun use of neuter plural of festus "festive, joyful, merry," related to feriae "holiday" and fanum "temple," from Proto-Italic *fasno- "temple," from PIE *dhis-no- "divine, holy; consecrated place," from *dhes- "root of words in religious concepts" [Watkins].

The spelling -ea- was used in Middle English to represent the sound we mis-call "long e." Meaning "abundant meal" (whether public or private) is by late 14c. Meaning "any enjoyable occasion or event" is from late 14c.