The creature known as the Dormouse is certainly not a dor, or beetle, nor related to anything that flies, nor is it exactly a mouse, though small and a member of the rodent family.
In fact, the source of its name has long been a matter of speculation and is still obscure, though in use for some five hundred years.
But because the animal is noted for sleepiness, the consensus is that the first element, dor, is from the same source as dormant, or, that is, from the Latin dormire “to sleep,” to which mouse was then added because of general appearance.