This word was formerly considered to be taboo, and it was labelled as such in previous editions of Collins English Dictionary. However, it has now become acceptable in speech, although some older or more conservative people may object to its use
C15 crappe chaff, from Middle Dutch, probably from crappen to break off
"defecate" 1846 (v.), 1898 (n.), from one of a cluster of words generally applied to things cast off or discarded (e.g. "weeds growing among corn" (1425), "residue from renderings" (1490s), 18c. underworld slang for "money," and in Shropshire, "dregs of beer or ale"), all probably from M.E. crappe "grain that was trodden underfoot in a barn, chaff" (c.1440), from M.Fr. crape "siftings," from O.Fr. crappe, from M.L. crappa, crapinum "chaff." Sense of "rubbish, nonsense" also first recorded 1898. Despite folk etymology insistence, not from Thomas Crapper (1837-1910) who was, however, a busy plumber and may have had some minor role in the development of modern toilets. The name Crapper is a northern form of Cropper (attested from 1221), an occupational surname, obviously, but the exact reference is unclear.
[by extension fr Middle English crap, ''chaff, siftings of grain, residue'']
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with crap out
Back down, quit, When it got to the point of putting up some money, Jack crapped out. This expression originated in the game of craps, where it means to make a first throw (of the dice) of two, three, or twelve, thereby losing.
[ ; 1920s
Go to sleep. This usage was military slang for sleeping during work hours or during a crap game.
[ ; c. 1940
Die, as in He's really sick; he could crap out any time. This usage is less common than def. 1 or def. 2.
[ ; 1920s