(1) An unsatisfactory bowel movement which produces a negligible amount of feces -- the stuff that barely dribbles out, and when it comes out, comes out measly 'kibbles-and-bits').
(2) By extension, an unsatisfying, negligible amount of anything.
(3) Something worthless produced after great effort; a "big nothing".
(1) ' America was . . . the richest and most powerful country on the planet.
' Most other countries didn't have doodley-squat.'
-- From Kurt Vonnegut's 1973 novel "Breakfast of Champions" -- Chapter 1 (page 12).
(2) 'Everybody in America was supposed to grab whatever he could and hold onto it. Some Americans were very good at grabbing and holding, were fabulously well-to-do. Others couldn't get their hands on doodley-squat.'
-- From "Breakfast of Champions" -- Ch. 1 (p. 13).
(3) ' Here is what they paid him: doodley-squat.'
-- From "Breakfast of Champions" -- Ch. 2 (p. 21).
(4) 'People took such awful chances with chemicals and their bodies because they wanted the quality of their lives to improve. They lived in ugly places where there were only ugly things to do. They didn't own doodley-squat, so they couldn't improve their surroundings. So they did their best to make their insides beautiful instead.
' The results had been catastrophic so far -- suicide, theft, murder, and insanity and so on.'
-- From "Breakfast of Champions" -- Ch. 8 (p. 71).
(5) ' He would be rendered destitute. He would become . . . an old man on . . . Skid Row. He would be by no means the only drifter of whom it could be truthfully said, "See him? Can you believe it? He doesn't have a doodley-squat now, but he used to be fabulously well-do-do." '
-- From "Breakfast of Champions" -- Ch. 24 (p. 280).