Origin and history of beastly

c. 1200, beste, "one of the lower animals" (opposed to man), especially "a four-footed animal," also "a marvelous creature, a monster" (mermaids, werewolves, lamia, satyrs, the beast of the Apocalypse), "a brutish or stupid man," from Old French beste "animal, wild beast," figuratively "fool, idiot" (11c., Modern French bête), from Vulgar Latin *besta, from Latin bestia "beast, wild animal," which is of unknown origin.

The word was used in Middle English to translate Latin animal. It displaced Old English deor (see deer) as the generic word for "wild creature," only to be ousted 16c. by animal.

suffix forming adjectives from nouns and meaning "having qualities of, of the form or nature of" (manly, lordly), "appropriate to, fitting, suited to" (bodily, earthly, daily); irregularly descended from Old English -lic, from Proto-Germanic *-liko- (Old Frisian -lik, Dutch -lijk, Old High German -lih, German -lich, Old Norse -ligr), related to *likom- "appearance, form" (Old English lich "corpse, body;" see lich, which is a cognate; see also like (adj.), with which it is identical).