In a Word: Of Mice and Muscle

Senior managing editor and logophile Andy Hollandbeck reveals the sometimes surprising roots of common English words and phrases. Remember: Etymology tells us where a word comes from, but not what it means today. 

Imagine, if you will, a toned young man hard at work. You watch as he lifts something heavy into place, and you notice the movement of certain masses beneath the skin of his arms and back. 

Now imagine that you don’t have the vocabulary yet to describe the internal parts of a person’s body because the field of anatomy hasn’t been invented yet — and you’re not about to slice this guy open to see how his arms work. So to come up with a name for something you don’t yet have a word for, you look to the vocabulary you do have and find some connection. 

That’s kind of how it was long, long ago. Some ancient Greeks thought the movement of muscles (particularly the bicepses, the big muscles in your arms) resembled a mouse — perhaps scurrying under a piece of cloth. So the word mys was used to mean both “mouse” and “muscle.” (Mys is the source of the prefix myo-, as in myocardium, the middle muscular layer of the heart, and myalgia, muscle pain or soreness.) 

The Latin-speaking Romans created a little more separation in the terminology — maybe after recognizing that mice have muscles too? They took their word for mouse, mus, and added a diminutive suffix, creating the word musculus. Musculus literally means “little mouse,” and it evolved into the English word muscle by the late 14th century. 

So, yes, the English words muscular and mousy (i.e., timid) are two evolved forms of the same word. 

The connection between muscles and mice isn’t limited to Greek- and Latin-based words, either. You can find the same type of linguistic relationship, either currently or historically, in Arabic, Cornish, German, Russian, Swedish, and a variety of other languages.