Meaning

noun small furry-tailed squirrel-like Old World rodent that becomes torpid in cold weather

originFrom Middle English dormowse, of uncertain origin. Possibly from a dialectal *dor-, from Old Norse dár (“benumbed”) + mous (“mouse”). More at doze, mouse. The word is sometimes conjectured to come from an Anglo-Norman derivative of Old French dormir (“to sleep”) (as *dormouse (“tending to be dormant”), with second element mistaken for mouse), but no such Anglo-Norman term is known to have existed.

Etymology from Wiktionary, CC BY-SA 3.0