A muscle is the tissue in the body that contracts to produce movement. A mussel is a bivalve shellfish. They are pronounced identically, and — unexpectedly — they are related: the shellfish was named for looking like a little mouse, and so was the muscle.
The core difference
Body tissue and a shellfish, pronounced the same and genuinely related.
- muscle — contractile body tissue: calf muscle. Figuratively: power or force.
- mussel — an edible bivalve: moules marinière.
The shared origin
Both come from Latin musculus, little mouse. A flexing muscle was thought to resemble a mouse moving under the skin, and the shellfish was named for its mouse-like shape. So the pair are not homophones by coincidence — they are the same word, twice.
The figurative muscle
Muscle means force or influence — political muscle, muscle in on. That sense is common and takes the body spelling, so "mussel in on a deal" is a shellfish attempting a takeover.
Frequently asked questions
Are muscle and mussel related?
Yes. Both come from Latin musculus, little mouse — the flexing tissue and the shellfish were each thought to resemble one.
Which spelling is the shellfish?
Mussel.
Why is a muscle named after a mouse?
A flexing muscle was thought to look like a small mouse moving beneath the skin.