A guy name named Jack had promised the Devil his soul as part of a deal and now saw a way out of it. He trapped the Devil up a tree by drawing crosses on the trunk. Jack made the Devil agree not to take his soul to Hell when he died before letting him down out of the tree. When Jack died, Heaven wouldn't have him because he'd trafficked with Satan and he wasn't allowed in Hell. He was forced to walk the Earth in limbo. To light his way, he hollowed out a turnip and put an ember in there to make a kind of lantern.