Actually, a Jack-o-lantern isn't the carved pumpkin itself. Jack-o-lantern, or Jack of the lantern, was actually a person in Irish folklore. Stingy Jack, as they called the man, invited the Devil to have a drink with him. Not wanting to pay for it himself, naturally, Jack asked the Devil to turn into a coin to pay for the drink, which the devil did. Jack then put him in his pocket next to a cross so he couldn't change back. Eventually, Jack let him out, making him promise to leave him alone for a year or so, and to not claim his soul if he died. So then a year's up, and he invites the Devil to pick fruit with him. The Devil, clearly either too thick or too hungover from last year's drink to see that this is a trap, climbs up the tree. Jack carved a cross in the trunk of the fruit tree so the Devil couldn't get out of it, and made him promise to leave him alone and not claim his soul for ten years, to which he again agrees. Jack dies at some point during this ten-year period. God didn't want him in Heaven, understandably, and the Devil couldn't take him, so be was banished to wander the earth forever in darkness, with only a carved turnip lantern for light. Every year, the Irish would carve turnips and potatoes to scare off Stingy Jack and other malevolent wandering spirits. When they came over here, they found pumpkins to be a lot sturdier, and so used those.