/ˈmʌs.əl/·noun·c. 1392–1400, Middle English 'muscle' in anatomical sense, attested in translations of medical texts from Latin·Established
Origin
From PIE *muh₂s through Latin *musculus* (little mouse) and parallel Greek *mûs*, 'muscle' preserves a Roman anatomist's observation that contracting tissue beneath skin resembles a mouse burrowing — the same word also gave English 'mussel', two spellings for one sign split by semantic pressure.
Definition
A band or bundle of fibrous tissue in the body that has the ability to contract, producing movement or maintaining the position of parts of the body.
The Full Story
LatinClassical Latin, 1st century BCE onwardwell-attested
The English word 'muscle' derives from Latin 'musculus', a diminutive of 'mus' meaning 'mouse'. The semantic motivation is vivid and well-attested: the rippling movement of a muscle beneath the skin was thought to resemble a mouse moving under a cloth. This metaphor is explicitlynoted by Roman writers; Pliny the Elder (Naturalis Historia, 1st century CE) and other classical authors used 'musculus' in this double sense. The Latin 'mus' (mouse) descends from Proto-Indo-European *muh₂s, a root meaning 'mouse' or 'thief' (possibly from a verb root meaning 'to steal', alluding to the mouse's pilfering habits
Did you know?
English 'muscle' and 'mussel' are the same word. Latin *musculus* named the shellfish and the bicep simultaneously — both seen as resembling a mouse or a mouse-shaped lump. Middle English inherited both senses as 'muscle' and only resolved the ambiguity by graduallyspelling the shellfish differently. There was no new word coined; English simply wrote its way out of an ambiguity that Latin held comfortably for centuries
to a mouse or small creature. The word entered Old French as 'muscle' and was borrowed into Middle English around the late 14th century. Scholarly sources: Ernout & Meillet, Dictionnaire étymologique de la langue latine; OED s.v. muscle; de Vaan, Etymological Dictionary of Latin. Key roots: *muh₂s (Proto-Indo-European: "mouse; possibly 'thief' or 'stealing creature'"), mus (Latin: "mouse"), musculus (Latin: "little mouse; muscle; mussel").