The truth is that no one is absolutely sure where the idea that Friday the 13th is unlucky originated. Donald Dossey, the founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina suspects the fear can be traced back to a Norse myth about twelve gods who had a dinner at Valhalla—the fabled hall where legendary Norse heroes feasted for eternity after they died—that was interrupted by a thirteenth guest, the evil and mischievous god Loki. According to legend, Loki tricked Höðr (the blind god of winter and son of Odin, the supreme god in Norse mythology) into shooting his brother Baldr (the benevolent god of summer who was also Odin’s son) with a magical spear tipped with mistletoe—the only substance that could defeat him. Thus the number thirteen was branded as unlucky because of the ominous period of mourning following the loss of such powerful gods by this unwanted thirteenth guest.
For whatever reason, among many cultures, the number twelve emerged throughout history as a "complete" number: There are twelve months in a year, twelve signs of the zodiac, twelve Gods of Olympus, twelve sons of Odin, twelve labors of Hercules, twelve Jyotirlingas or Hindu shrines where Shiva is worshipped, twelve successors of Muhammad in Shia Islam, and twelve tribes of Israel. In Christianity, Jesus was betrayed by one of his twelve Apostles—Judas—who was the thirteenth guest to arrive for the Last Supper. Surpassing the number twelve ostensibly unbalances the ideal nature of things; because it is seen as irregular and disrespectful of a sense of perfection, the number thirteen bears the stigma of misfortune and bad luck we know today.
