Webster’s Revised Unabridged Dictionary · 1913
Buttock
But′tock (bŭt′tŭk), n. [From Butt an end.] 1. The part at the back of the hip, which, in man, forms one of the rounded protuberances on which he sits; the rump.
2. (Naut.) The convexity of a ship behind, under the stern. Mar. Dict.