A do-do usually refers to an
immature penis, but it can and is used to also, as a pejorative, to identify or describe the shrinking or
always very
small penis of an older or elderly white man.
Come on,
Bobby, stand next to the toilet like Daddy and
aim your do-do, right in the middle, try to hit the toilet paper.
I am sorry
honey, Grandma is too tired to play with Grandpa's do-do, you play with it.