"fabricate, devise," 1690s, from trump "deceive, cheat" (1510s), from Middle English trumpen (late 14c.), from Old French tromper "deceive," of uncertain origin, perhaps from a verb meaning "to blow a trumpet." Related: Trumped; trumping. Trumped up "false, concocted" first recorded 1728.
"trumpet," c.1300, from Old French trompe "long, tube-like musical wind instrument" (12c.), cognate with Provençal tromba, Italian tromba, all probably from a Germanic source (cf. Old High German trumpa and Old Norse trumba "trumpet"), of imitative origin.