mid-14c., flappe "a blow, slap," probably imitative of the sound of striking. Meaning "something that hangs down" is first recorded 1520s. Sense of "motion or noise like a bird's wing" is 1774; meaning "disturbance, noisy tumult" is 1916, British slang.
early 14c., "dash about, shake;" later "strike, hit;" see flap (n.). Meaning "to swing loosely" is from 1520s. Related: Flapped; flapping.
flap (flāp)
n.
Tissue used in surgical grafting that is only partially detached from its donor site so that it continues to be nourished during transfer to the recipient site.
To become flustered; lose one's composure: I've seen him under hostile pressure before. He doesn't flap and he doesn't become a doormat (1920s+)
A symbolic mathematics package for IBM 360.
["FLAP Programmer's Manual", A.H. Morris Jr., TR-2558 (1971) US Naval Weapons Lab].
[Sammet 1969, p. 506].
[Jargon File]
(1994-10-17)