Dormice can hibernate six months out of the year, or even longer if the weather does not become warm enough, sometimes waking for brief periods to eat food they had previously stored nearby. During the summer, they accumulate fat in their bodies to nourish them through the hibernation period.

English dormouse from Middle English dormous, of uncertain origin. Possibly from a dialectal *dor-, from Old Norse dár 'benumbed' + mous '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.