The woods are fucking scary. I just spent a weekend in the woods up a tree and I can confirm. Imagine you're some moron who can't read, living in a time like 400 years before science and reason were invented. You walk into the woods and you hear a twig snap behind and that could be anything. Sure, it could be a squirrel, but when you turn around and there's no squirrel then your mind is off to the races. Could be a wolf, a bear, a dragon, a witch, a ghost, or worst of all...another human being looking to rob, rape, and/or murder you. You go for a walk in the woods and you take your life in your hands. The woods have always been the fucking scariest thing going and that is why it has seeped into our language and lexicon for a thousand years.