Using pumpkins as lanterns at Halloween is based on an ancient Celtic custom brought to America by Irish immigrants. All Hallows Eve on 31 October marked the end of the old Celtic calendar year, and on that night hollowed-out turnips, beetshttp://en.wikipedia.org/wiki/Beet and rutabagas with a candle inside were placed on windowsills and porches to welcome home spirits of deceased ancestors and ward off evil spirits and a restless soul called "Stingy Jack," hence the name "Jack-o'-lantern".