Fear of Friday the 13th
So where does it come from — the fear of 13? Its origins can be traced to Norse mythology and a dinner party at Valhalla, home of the god Odin, where Odin and 11 of his closest god-friends were gathered one night to party. Everyone was having fun, but then Loki, the dastardly god of evil and turmoil, showed up uninvited, making it a crowd of 13. The beloved god Balder tried to boot Loki out of the house, the legend goes, and in the scuffle that followed he suffered a deathblow from a spear of mistletoe.
From that mythological start, the number 13 has plowed a path of devastation through history. There were 13 people at Christ’s Last Supper, including the double-crossing Judas Iscariot. The ill-fated Apollo 13 lunar mission left the launching pad at 13:13 hours and was aborted on April 13. Friday hasn’t been much kinder to us. Friday was execution day in ancient Rome — Jesus was crucified on a Friday. Put it all together, and Friday the 13th spells trouble for triskaidekaphobics. It’s a testament to the phobia’s prevalence that Hollywood was able to parlay our fear into a hugely successful series of slasher movies starring a hockey-masked guy named Jason.
But triskaidekaphobia isn’t an exclusively American affliction. Italians omit the number 13 from their national lottery. There is a hush-hush organization in France whose exclusive purpose is to provide last-minute guests for dinner parties, so that no party host ever has to suffer the curse of entertaining 13 guests.
— Excerpted from Jon Bowen, writing at Slate.