means A body tissue made of fibers that contract to produce movement or force, often used figuratively for physical strength or coercive power.

from From Latin 'musculus,' meaning 'little mouse' — the diminutive of 'mus' (mouse) — because a flexed bicep, rippling under the skin, looked to Roman eyes like a small mouse darting beneath the surface. The word strolled into English through French in the late Middle Ages, still carrying its rodent in tow.