The word "muscle" comes from the Latin word musculus, which literally translates to “a little mouse.” Why? It was once thought that the shape and movement of some human muscles, especially the biceps, resembled mice moving under the skin. This is also reflected in the Greek word mys, which means both "mouse" and "muscle.”

People today are perhaps unlikely to think of their muscles as resembling mice. The ancient Romans, however, saw a likeness, especially in the major muscles of the arms and legs. For that reason the Latin word musculus, which originally meant "little mouse," came to be used to mean "muscle."