"playing card of a suit ranking above others," 1529, alteration of triumph, name of a card game. The verb meaning "surpass, beat" is attested from 1586.
"fabricate, devise," 1695, from trump "deceive, cheat" (1513), from M.E. trumpen (late 14c.), from O.Fr. tromper "deceive," of uncertain origin, perhaps from a verb meaning "to blow a trumpet." Trumped up "false, concocted" first recorded 1728.
"trumpet," c.1300, from O.Fr. trompe "long, tube-like musical wind instrument" (12c.), cognate with Prov. tromba, It. tromba, all probably from a Gmc. source (cf. O.H.G. trumpa and O.N. trumba "trumpet"), of imitative origin.
Concoct fraudulently, fabricate, as in They trumped up a charge of conspiracy, or She had trumped up another excuse for not doing the work. This expression, first recorded in 1695, uses trump in the sense of “devise fraudulently,” a usage otherwise obsolete.