MUSSEL

noun Etymology: Middle English muscle, from Old English muscelle, from Vulgar Latin *muscula, from Latin musculus muscle, ~ Date: before 12th century a marine bivalve mollusk (especially genus Mytilus ) usually having a dark elongated shell, a freshwater bivalve mollusk (as of Unio, Anodonta, or related genera) that is especially abundant in rivers of the central United States and has a shell with a lustrous nacreous lining