I visited a friend named S. in the hospital yesterday who was going to get his bone marrow sampled. To do this, the doctors bore into the hip bone in S.’s butt. (It’s not as bad as it sounds.) Since the doctors had trouble boring through that bone, S. said:
“I guess that proves that I’m a hard-ass.”
BTW, other words for a pain in the butt include rectalgia, proctalgia, and proctodynia. Want to say someone has a hairy butt? Go with dasypygal. Or an ugly butt? That’d be cacopygian.