fell (v.1)

Old English feallan (class VII strong verb; past tense feoll, past participle feallen) "to drop from a height; fail, decay, die," from Proto-Germanic *fallanan (source also of Old Frisian falla, Old Saxon fallan, Dutch vallen, Old Norse falla, Old High German fallan, German fallen, absent in Gothic).

These are from PIE root *pol- "to fall" (source also of Armenian p'ul "downfall," Lithuanian puolu, pulti "to fall," Old Prussian aupallai "finds," literally "falls upon").

The meaning "come suddenly to the ground" is from late Old English. Of darkness, night, from c. 1600; of land sloping from 1570s; of prices from 1570s. Of empires, governments, etc., from c. 1200. Of the face or countenance from late 14c. The meaning "to be reduced" (as temperature) is from 1650s. That of "die in battle" is from 1570s. The meaning "to pass casually (into some condition)" is from early 13c.

To fall in "take place or position" is from 1751. To fall in love is attested from 1520s; to fall asleep is late 14c. (Middle English also used slide asleep, etc.). To fall down is early 13c. (a-dun follon); to fall behind is from 1856. Fall through "fail, come to nothing" is from 1781. To fall for something is from 1903.

To fall out is by mid-13c. in a literal sense; military use is from 1832. The meaning "have a disagreement, begin to quarrel" is attested from 1560s (to fall out with "quarrel with" is from late 15c.).

c. 1300, feloun, "one who deceives or commits treason; one who is wicked or evil; evil-doer," used of Lucifer and Herod, from Old French felon "evil-doer, scoundrel, traitor, rebel, oath-breaker, the Devil" (9c.), from Medieval Latin fellonem (nominative fello) "evil-doer," which is of uncertain origin, perhaps from Frankish *fillo, *filljo "person who whips or beats, scourger" (source of Old High German fillen "to whip"); or from Latin fel "gall, poison," on the notion of "one full of bitterness." Celtic origins also have been proposed.

Another theory (advanced by Professor R. Atkinson of Dublin) traces it to Latin fellare "to suck" (see fecund), which had an obscene secondary meaning in classical Latin (well-known to readers of Martial and Catullus), which would make a felon etymologically a "cock-sucker." OED (1989) inclines toward the "gall" explanation, but finds Atkinson's "most plausible" of the others.

Also by c. 1300 in English in a general legal sense "criminal; one who has committed a felony," however that was defined. Century Dictionary notes, "the term is not applicable after legal punishment has been completed." In Middle English it also was an adjective, "traitorous, wicked, malignant." Compare traitor for sense development. Australian official James Mudie (1837), coined felonry "as the appellative of an order or class of persons in New South Wales,—an order which happily exists in no other country in the world."