"stern deck of a ship," c.1400, from Middle French poupe "stern of a ship" (14c.), from Old Provençal or Italian poppa, from Latin puppis "poop, stern," of uncertain origin. Poop deck attested by 1779.
"excrement," 1744, a children's euphemism, probably of imitative origin. The verb in this sense is from 1903. Cf. the same word in the sense "to break wind softly," attested from 1721, earlier "to make a short blast on a horn" (late 14c.). Meaning "stupid or dull person" is from 1915. Pooper-scooper attested from 1970.
"up-to-date information," 1941, in poop sheet, U.S. Army slang, of unknown origin, perhaps from poop (n.2).
"become tired," 1931, of unknown origin (see pooped). Related: Pooping.
"tired," 1931, of unknown origin, perhaps imitative of the sound of heavy breathing from exhaustion (cf. poop (n.2)). But poop, poop out were used in 1920s in aviation, of an engine, "to die." Also there is a verb poop, of ships, "to be overwhelmed by a wave from behind," often with catastrophic consequences (see poop (n.1)); hence in figurative nautical use, "to be overcome and defeated" (attested in 1920s).
It is an easy thing to "run"; the difficulty is to know when to stop. There is always the possibility of being "pooped," which simply means being overtaken by a mountain of water and crushed into the depths out of harm's way for good and all. [Ralph Stock, "The Cruise of the Dream Ship," 1921]
[probably fr a merging of 14th-century poupen, ''to toot,'' with 15th-century poop, ''the rear part of a ship,'' fr Latin puppis of the same meaning; the fatigue sense may be related to the condition of a ship that is pooped, ''has taken a wave over the stern'']