mid-15c., "to escheat, to seize as an escheat," a shortening of Old French escheat, legal term for revision of property to the state when the owner dies without heirs, literally "that which falls to one," past participle of escheoir "happen, befall, occur, take place; fall due; lapse (legally)," from Late Latin *excadere "fall away, fall out," from Latin ex- "out" (see ex-) + cadere "to fall" (from PIE root *kad- "to fall").
Also compare escheat. The royal officers who had charge of escheats evidently had a reputation for unscrupulousness, and the meaning of the verb evolved through "confiscate" (mid-15c.) to "deprive unfairly" (1580s), to "deceive, impose upon, trick" (1630s). Intransitive sense "act dishonestly, practice fraud or trickery" is from 1630s. To cheat on (someone) "be sexually unfaithful" is attested by 1934. Related: Cheated; cheating.
late 14c., "forfeited property, reversion of property to a lord," from cheat (v.) or from escheat (n.). Meaning "a fraud committed by deception, a deceptive act" is from 1640s; earlier, in thieves' jargon, it meant "a stolen thing" (late 16c.), and earlier still "dice" (1530s). It also was used in canting slang generally, as an affix, for any "thing" (e.g. cackling-chete "a fowl," crashing-chetes "the teeth"). Meaning "a swindler, a person who cheats" is from 1660s; from 1680s as "anything which deceives or is intended to deceive."
It forms all or part of: accident; cadaver; cadence; caducous; cascade; case (n.1); casual; casualty; casuist; casus belli; chance; cheat; chute (n.1); coincide; decadence; decay; deciduous; escheat; incident; occasion; occident; recidivist.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit sad- "to fall down;" Latin casus "a chance, occasion, opportunity; accident, mishap," literally "a falling," cadere "to fall, sink, settle down, decline, perish;" Armenian chacnum "to fall, become low;" perhaps also Middle Irish casar "hail, lightning."
"to cheat, defraud," 1560s, of uncertain origin; perhaps from French cousiner "cheat on pretext of being a cousin;" or from Middle English cosyn "fraud, trickery" (mid-15c.), which is perhaps related to Old French coçon "dealer, merchant, trader," from Latin cocionem "horse dealer." Related: Cozened; cozening; cozenage.