Grandpa's Ligma

Alright, listen up, buttercup. This joke is a play on words. "Ligma" sounds like "lick my," so when the author says their grandpa died of "ligma," they're setting you up to ask, "What's ligma?" And then BAM! They hit you with the ol' "lick my balls." It's a childish prank, but hey, some folks find it hilarious. And by some folks, I mean dumb-dumbs like you.