crap (v.)youdaoicibaDictYouDict
"defecate," 1846, from one of a cluster of words generally applied to things cast off or discarded (such as "weeds growing among corn" (early 15c.), "residue from renderings" (late 15c.), underworld slang for "money" (18c.), and in Shropshire, "dregs of beer or ale"), all probably from Middle English crappe "grain that was trodden underfoot in a barn, chaff" (mid-15c.), from Middle French crape "siftings," from Old French crappe, from Medieval Latin crappa, crapinum "chaff." Related: Crapped; crapping.

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. Crap (v.) as a variant of crop (v.) was noted early 19c, as a peculiarity of speech in Scotland and the U.S. Southwest (Arkansas, etc.).
Draw out yere sword, thou vile South'ron!
Red wat wi' blude o' my kin!
That sword it crapped the bonniest flower
E'er lifted its head to the sun!

[Allan Cunningham (1784-1842), "The Young Maxwell"]
interest (n.)youdaoicibaDictYouDict
mid-15c., "legal claim or right; concern; benefit, advantage;" earlier interesse (late 14c.), from Anglo-French interesse "what one has a legal concern in," from Medieval Latin interesse "compensation for loss," noun use of Latin interresse "to concern, make a difference, be of importance," literally "to be between," from inter- "between" (see inter-) + esse "to be" (see essence).

Compare German Interesse, from the same Medieval Latin source. Form in English influenced 15c. by French interest "damage," from Latin interest "it is of importance, it makes a difference," third person singular present of interresse. Financial sense of "money paid for the use of money lent" (1520s) earlier was distinguished from usury (illegal under Church law) by being in reference to "compensation due from a defaulting debtor." Meaning "curiosity" is first attested 1771. Interest group is attested from 1907; interest rate by 1868.