Why are pumpkins also known as 'Jack-o-Lanterns'?

The name "Jack O'Lantern" comes from an old Irish folktale. Stingy Jack led a life of debauchery and even managed to fool and trap the Devil twice. Well, when Jack died he was not allowed into Heaven and the Devil wouldn't let him into Hell, so Jack was forced to wander the earth with a single lit coal for warmth and light which he carried in a hollowed-out turnip. The story of Jack of the Lantern, now Jack O'Lantern, inspired the Irish to carve turnips at Halloween, a practice they brought to America where they found pumpkins much easier to carve.