She has stated that her stage forename (“Whoopi”) was taken from a whoopee cushion: “When you’re performing on stage, you never really have time to go into the bathroom and close the door. So if you get a little gassy, you’ve got to let it go. So people used to say to me, ‘You’re like a whoopee cushion.’ And that’s where the name came from.”
https://en.m.wikipedia.org/wiki/Whoopi_Goldberg

TIL it was a fart joke.