c. 1200, "to torment or persecute (someone);" c. 1300, "to set a dog to bite and worry (an animal, especially a confined one, for sport)," from Old Norse beita "to cause to bite," from Proto-Germanic *baitjan (source also of Old English bætan "to cause to bite," Old High German beizzen "to bait," Middle High German beiz "hunting," German beizen "to hawk, to cauterize, etch"), causative of *bitan (see bite (v.)).
The earliest attested use is figurative of the literal one, which is from the popular medieval entertainment of setting dogs on some ferocious beast to bite and worry it. The verb also in Middle English could mean "put a horse or other domestic beast out to feed or graze," and, of persons, "to eat food," also figuratively "feast the eye" (late 14c.). Compare bait (n.). Related: Baited; baiting.
Half-wits are fleas; so little and so light,
We scarce could know they live, but that they bite.
[Dryden, "All for Love"]
Phrase out of half wit "half out of one's mind" was in Middle English (late 14c.). Half-witted "lacking common sense" is from 1640s.
dog sound, Old English beorc, from bark (v.). Paired and compared with bite (n.) at least since 1660s; the proverb is older: "Timid dogs bark worse than they bite" was in Latin (Canis timidus vehementius latrat quam mordet, Quintius Curtius).
Middle English smerten, "to cause pain, to suffer pain," from Old English smeortan "be painful," in reference to wounds, from Proto-Germanic *smarta- (source also of Middle Dutch smerten, Dutch smarten, Old High German smerzan, German schmerzen "to pain," originally "to bite"). The Germanic word is perhaps cognate with Latin mordēre "to bite, bite into," figuratively "to pain, cause hurt," and both might be from an extended form of PIE root *mer- "to rub away, harm." Usually of a lively, pungent, local pain. Related: Smarted; smarts; smarting.
also philter, "love potion, potion supposed to have the power of exciting sexual love," 1580s, from French philtre (1560s), from Latin philtrum (plural philtra) "love potion," from Greek philtron "a love-charm," properly philētron, literally "to make oneself beloved," from philein "to love" (from philos "loving;" see philo-) + instrumental suffix -tron.
c. 1300, "love," from Old French amor "love, affection, friendship; loved one" (11c.), from Latin amor "love, affection, strong friendly feeling" (sometimes used of feelings for sons or brothers, but it especially meant sexual love), from amare "to love" (see Amy). The accent shifted 15c.-17c. to the first syllable as the word became nativized, then shifted back as the sense "illicit love affair" became primary 17c. and the word was felt to be an imported euphemism.
A common ME word for love, later accented ámour (cf. enamour). Now with suggestion of intrigue and treated as a F[rench] word. [Weekley]