hibernaculum

If you're afraid of snakes or bats, you probably won't enjoy thinking about a hibernaculum, where hundreds, even thousands, of these creatures might be passing the wintry months. Other creatures also use hibernacula, though many of these tend to be a bit inconspicuous. The word hibernaculum has been used for the burrow of a woodchuck, for instance, as well as for a cozy caterpillar cocoon attached to a wintry twig, and for the spot in which a frog has buried itself in the mud. Hibernacula are all around us and have been around for a long, long time, but we have only called them such since 1789. In case you are wondering, "hibernate" didn't come into being until the beginning of the 19th century. Both words come from Latin hibernare, meaning "to pass the winter."