All Fowler proves is that 13 was considered an unlucky number, a tradition that may go back to ancient mythology. According to Donald Dossey, author of "Holiday Folklore, Phobias and Fun" (Outcome Unlimited Pr, 1992), a Norse myth told of a dinner party for 12 gods at which a 13th guest showed up uninvited. The gatecrasher — the trickster god Loki — shot the god of joy and happiness, Balder. The Christian tale of the Last Supper likewise holds Judas, Jesus' betrayer, as the "unlucky" 13th guest.