A small dormouse on a tree branch.
dormouse definition by Webster's New World
Origin: Middle English dormous uncertain or unknown; perhaps altered by folk etymology (after mous, mouse) ; from Old French dormeuse, sleepy, sluggish ; from dormir: see dormant
dormouse definition by American Heritage Dictionary
Origin: Middle English, probably alteration (influenced by mous, mouse) of Anglo-Norman dormeus, inclined to sleep, hibernating, from Old French dormir, to sleep; see dormant.