in card-playing, "act of trumping when a player has no cards of the suit led," by 1856, from ruff (v.) "trump when unable to follow suit" (1760), from the name of the old game of ruff (1580s), from French roffle, earlier romfle (early 15c.), from Italian ronfa, which is perhaps a corruption of trionfo "triumph" (from French; compare trump (n.1)). The old game, a predecessor of whist, was in vogue c. 1590-1630.
"fabricate, devise," 1690s, from trump "deceive, cheat" (1510s), from Middle English trumpen (late 14c.), from Old French tromper "to deceive," of uncertain origin. Apparently from se tromper de "to mock," from Old French tromper "to blow a trumpet." Brachet explains this as "to play the horn, alluding to quacks and mountebanks, who attracted the public by blowing a horn, and then cheated them into buying ...." The Hindley Old French dictionary has baillier la trompe "blow the trumpet" as "act the fool," and Donkin connects it rather to trombe "waterspout," on the notion of turning (someone) around. Connection with triumph also has been proposed. Related: Trumped; trumping. Trumped up "false, concocted" first recorded 1728.