“Hoary” has several usages with slight variations on a theme: describing something old, white, or gray. Most of its meanings relate to age and color (for example, a hoary white beard), or at least something outdated, but it’s also used as an attributive word for several animal species. The hoary bat, for instance, gets its name from whitish-gray fur markings across its body, which give it the appearance of an old and wizened creature.