Do you know "Jack"?
The most likely origin of the practice of Jack o Lanterns was an imitation of the old moralistic Irish folktale of Jack, the conniving drunk who tricks the devil into rejecting his soul, and upon death is forced to wander forever, not welcome in heaven nor hell. The "jack o lantern" is the hollowed turnip he carries as a lamp, with a lump of hell's coal lighting his path as he endlessly wanders the earth.