pratfall (n.)

c. 1200, "a falling to the ground; a dropping from a height, a descent from a higher to a lower position (as by gravity); a collapsing of a building," from Proto-Germanic *falliz, from the source of fall (v.). Old English noun fealle meant "snare, trap."

Of the coming of night from 1650s. Meaning "downward direction of a surface" is from 1560s, of a value from 1550s. Theological sense, "a succumbing to sin or temptation" (especially of Adam and Eve) is from early 13c.

The sense of "autumn" (now only in U.S. but formerly common in England) is by 1660s, short for fall of the leaf (1540s). Meaning "cascade, waterfall" is from 1570s (often plural, falls, when the descent is in stages; fall of water is attested from mid-15c.). The wrestling sense is from 1550s. Of a city under siege, etc., 1580s. Fall guy is attested by 1906.

"buttock," 1560s, criminals' slang, of unknown origin. Later in U.S. criminal slang, "hip pocket" (1914), and in British slang "contemptible person" (1968).