What Is the Origin of ‘the Worm Has Turned’?

A friend asked me the other day about the origin of the phrase the worm has turned. I was too embarrassed to admit that not only did I not know the origin, I wasn’t even sure what the proverb meant. “It probably started with Shakespeare,” I said, hoping to sound more learned than I felt.

My friend’s husband got in on the discussion with the idea that worms were turning as they chewed their way through old books — that we were, in other words, talking about bookworms.* Challenged, he looked up t...