Bump and Grind.
I have heard the expression since I was a youngster.
I have seen exotic dancers do it. There’s even a new Fanta commercial
being played during Wimbledon Tennis coverage in which a bunch of young
ladies do a teeny-bopper rendition of it. (You’ll know it when you see it, and
when you do, you might even wonder how it got past the censors.)
But I have to confess I don’t know where the bump starts and the grind begins,
or vice versa.