also pooh, baby-talk for "excrement," 1950s (see poop (n.2)).
Entries linking to poo
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.