do one's duty

From doo-doo, doody, etc. used as euphemisms for shit.

do one's duty

1. (euphemistic) Synonym of use the toilet: to urinate or defecate.
   • 1996, Derrick Humphreys, ‎John A. Munro, The making of a grey panther: the Derrick Humphreys story, page 8:

     And when I was being toilet-trained as a very little boy, she'd always ask, "Have you done your duty?" That was the word for it.

   • 2012, Alan Watts, Zen and the Beat Way:

     If a society is incapable of that kind of trust, it is also incapable of freedom. But if one really believes that only productivity can create strength — that a human being, in other words, has to justify himself or herself by producing something — then maybe the psychoanalysts are right, and everything does go back to toilet training and mother's saying, "Have you produced today, have you done your duty?"

2. Used other than with a figurative or idiomatic meaning: see do,‎ duty.

• Used by caregivers when toilet-training young children.

• See use the toilet, Thesaurus:urinate, and Thesaurus:defecate