Old English muscle, musscel "shellfish, mussel," from Late Latin muscula (source of Old French musle, Modern French moule, Middle Dutch mosscele, Dutch mossel, Old High German muscula, German Muschel), from Latin musculus "mussel," literally "little mouse," also "muscle;" like muscle, derived from mus "mouse" on the perceived similarity of size and shape. The modern spelling, distinguishing the word from muscle, first recorded c.1600, not fully established until 1870s.