A butt may refer to:

-the buttocks in U.S. slang.
-Butt joint, a woodworking joinery technique
-a person mocked or embarrassed by a joke: the butt of a joke
-a pork shoulder in butchery; people sometimes say Boston butt or simply pork butt

Babies got back

But(t) i prefer this article from April 18, 1977 :

The President-to-be suffered an “anal fixation” too. The evidence cited for this–e.g., his scatological remarks–would doom every G.I. and fraternity man. With both fixations at work, Abrahamsen solemnly concludes, “there could be tittle or no emotional growth.” For a Freudian the early years are all-important, and the pivotal personality in Nixon vs. Nixon is his mother. Hannah, whom the President described as a saint in his tearful televised farewell to the White House with the enormous Baby got back.

Thanks to Wikipedia, Sir Mix Alot and Nixon.

Baby got back

Baby got back