flop (n.)

1823, "act of flopping; any action that produces the sound 'flop;' the sound itself," from flop (v.). Figurative sense of "a failure; that which is a failure" is by 1893, from the notion of a sudden break-down or collapse. Extended form flopperoo attested from 1936. The Fosbury flop high-jumping technique (1968) is so called in reference to U.S. athlete Dick Fosbury (b.1947), who used it to win the 1968 Olympic gold medal.

flop (v.)

c. 1600, "to flap," probably a variant of flap with a duller, heavier sound. Sense of "fall or drop heavily" is 1836; that of "collapse, fail" is 1919; though the figurative noun sense of "a failure" is recorded from 1893. Related: Flopped; flopping.