The term Jack of the Lantern refers to a night watchman or a man carrying a lantern.  It was also used to describe a strange light flickering over the marshes of Ireland.  If approached, the light advanced and was always out of reach.  The mysterious occurrence is also known as will o' the wisp.  However, in Irish folklore, legend states it is a stingy drunkard named Jack.  

      Jack, an Irish blacksmith, ran into the Devil in a pub on Halloween. Jack had already had a bit too much to drink that evening. He almost fell prey to the Devil, but Jack was quick witted and instead made a bargain with the Devil.  In exchange for one last drink, Jack offered up his soul.  The Devil changed his form into a sixpence in which to make payment to the bartender, but Jack pocketed the coin in a bag with a silver cross with the knowledge that the Devil couldn't revert form.  Once under Jack's thumb, and in his purse, the Devil agreed not to come for Jack's soul for another ten years.  

     Ten years went by and the Devil came looking for Jack.  He found him walking down a country road.  Jack, still quick witted and a trickster, asked for one last apple before he went with the Devil.  The Devil agreed and climbed an apple tree to get an apple for Jack.  As soon as the Devil went up Jack carved the sign of the cross in the tree so the Devil couldn't come down.