How Well Do You Know English Slang?
1926, echoic of the sound of a heavy blow or something falling heavily.
1952, from whomp (n.). Related: Whomped; whomping.
To make; devise or build: I whomped me up one heck of a nightmare (1950+)
[echoic fr the sound of a blow, perhaps influenced by dialect whup and whop, ''whip'']