Remembered the phrase "[someone] is turning in his grave", as a way of saying that someone who's now dead would so deeply disapprove of something that a living person is doing that their corpse would stir in unease.
Then I remembered an expression, "even a worm will turn", as a way of saying that no matter how downtrodden or lowly someone seems, they can nonetheless turn against their abusers and oppressors once they've had enough of it.
Then cross-contamination happened and the phrase "a worm is turning in his grave" emerged to me. I have no idea what that means.