A “muscle” is a little mouse

Flex your bicep and watch it move under the skin. The Romans thought it looked like a mouse, so that's what they named it.

Flex your bicep and watch it bunch up and slide around under the skin. Now picture a small animal doing that. The Romans did, and they landed on one: a mouse. Muscle comes from Latin musculus — literally "little mouse."

The etymology of “muscle”

It wasn't just the Romans, either. The Greeks made the exact same leap: their word mys meant both "mouse" and "muscle." Two cultures, same body part, same little rodent. Something about a flexing muscle just reads as a mouse burrowing under the surface.

The mouse left one more fingerprint. That same musculus also gave us mussel, the shellfish, named apparently for being small and mouse-shaped too. The two words were spelled every which way for centuries before English finally split them: muscle for the arm, mussel for the shell.

So your muscles are a whole nest of little mice, and dinner might be one as well.