Poop
late Middle English: from Old French pupe, from a variant of Latin puppis ‘stern’.
wiktionary
Origin uncertain, possibly from Middle English poupen(“to make a gulping sound while drinking, blow on a horn, toot”). Compare Dutch poepen(“to defecate”), German Low German pupen(“to fart; break wind”).
Recorded in World War II (1941) Army slang poop sheet(“up-to-date information”), itself of uncertain origin, perhaps toilet paper referring to etymology 2.
Origin uncertain, perhaps sound imitation.
From Middle English poupe, pope, from Old French pope, poupe, pouppe, from Italian poppa, from Vulgar Latin *puppa, from Latin puppis, all meaning “stern of a ship”.
Origin uncertain, perhaps a shortening of nincompoop.
etymonline
poop (n.1)
"stern or aftermost deck of a ship," c. 1400, from Old French poupe "stern of a ship" (14c.), from Old Provençal or Italian poppa, from Latin puppis "poop, stern," a word of uncertain origin. Also "a deck above the ordinary deck on the aftermost part of a ship." As a verb, "to break heavily over the stern of a ship" (of waves, etc.). Poop deck is attested by 1779.
poop (n.2)
"excrement," 1744, a children's euphemism, probably of imitative origin. The verb in this sense is from 1903, but the same word in the sense "to break wind softly" is attested from 1721; earlier "to make a short blast on a horn" (poupen, late 14c.). Meaning "stupid or dull person" is from 1915, but this is perhaps short for nincompoop. Pooper-scooper is attested from 1970.
poop (n.3)
"up-to-date information," 1941, in poop sheet, U.S. Army slang, of unknown origin, perhaps from poop (n.2).
poop (v.)
"become tired," 1931, of unknown origin (see pooped). With out (adv.) by 1934. Related: Pooping.
