In Celtic mythology they’re known as “fairy cattle”
The word deer comes from dēor and der, which in old and middle English meant, simply, “animal”. The Dutch word “dier” still means this. The sense of a deer as an animal, as opposed to a human – it has been found to have referred to ants, fish and foxes – may come from “wilddēornes”, the origin of wilderness or wild-animal-ness.
Deer still seem to embody this mysterious animal-ness: four-legged wildness, dainty and strong, mysterious and controlled. You may say it is all in the antlers: I say it is all in the tail. I saw a small herd of fallow deer in London’s Clissold park recently. A doe walked up to the fence as I walked past, then turned away and flicked her white tail: a flash of white, like a shooting star you’re not sure you’ve seen, like the tap of a fluffy wand, like a cute cursor blinking.