The superstition
Triskaidekaphobia is the fear of the number 13. It is less a clinical phobia than a cultural habit: dinner parties of thirteen are broken up, hotels and office towers skip from the 12th floor to the 14th, airlines drop row 13, and Friday the 13th is treated as a day to stay home. The question is where any of this came from, and the honest answer is that most of the popular origin stories were attached to the number long after people had started avoiding it.
The usual origins
The oldest claim is that the Code of Hammurabi, the Babylonian law code of around 1750 BCE, omits a thirteenth law. It does not. The original stele has no numbering at all. The gap comes from L. W. King’s English translation of 1910, which jumps from law 12 to law 14; the clause that should sit between them, about a seller who has died before a dispute is settled, was simply folded in. The Yale Law School’s online copy of King’s text still shows the jump, which is how the myth keeps renewing itself.
The Christian account points to the Last Supper, with Judas as the thirteenth at the table, and the Norse account to the trickster Loki arriving as the uninvited thirteenth guest at a feast of the gods and engineering the death of Balder. Nathaniel Lachenmeyer, who traced the superstition for his 2004 book 13, found that the Norse story survives only in texts written down in Christian times and may itself have been shaped by the Last Supper. The earliest clear reference he found to thirteen at table being unlucky is from the Earl of Rochester in 1680. Before that, thirteen was no worse than any other number.
Friday the 13th is younger still. Friday was unlucky on its own, as the day of the Crucifixion and the traditional day for hangings; thirteen was unlucky on its own. The two were combined in print, as far as anyone has found, only in 1907, in a novel by the Boston stock promoter Thomas W. Lawson titled Friday, the Thirteenth, about a broker who picks the date to crash the market.
The Thirteen Club
In 1881 a Civil War veteran named William Fowler, who ran a tavern called the Knickerbocker Cottage on Sixth Avenue in Manhattan, set out to kill the superstition by mocking it. Fowler had attended Public School 13, put up 13 buildings as an architect, fought in 13 engagements and belonged to 13 clubs, and had come through it all fine. According to the club’s own records, now at the New York Public Library, his Thirteen Club held its first dinner in room 13 of the Cottage on September 13, 1881, with 13 at table, 13 candles, 13 toasts and a banner reading “we who are about to die salute you”. Later accounts give the date as Friday, January 13. Members entered under a ladder, spilled salt, broke mirrors, ate lobster salad molded into coffins and held mock trials of anyone caught being superstitious. The press loved it. Chapters opened in Chicago, London and Paris; the club lobbied judges to stop scheduling hangings on Fridays, and it collected honorary members including Chester A. Arthur, Grover Cleveland and Theodore Roosevelt. Nobody died at a faster rate than the general population, and the club carried on into the twentieth century.
The evidence
Whether 13 brings bad luck can be tested, and it has been, mostly for fun. A 1993 paper in the Christmas issue of the British Medical Journal compared Friday the 6th with Friday the 13th in one English health region and found fewer cars on the M25 but more hospital admissions for transport accidents on the 13th, 65 against 45, which the authors used to recommend staying at home. Later and larger studies of emergency-room visits, surgical outcomes and accident rates have found no difference on the date. The one measurable effect of the number is on behavior: people avoid it, and businesses accommodate them.
Where it stands
Thirteen is unlucky because people believe it is unlucky, and the belief has a history that runs back to the late seventeenth century rather than to Babylon or Valhalla. The missing Hammurabi law, the Norse origin and the ancient pedigree of Friday the 13th are all later inventions. The verdict is legend: a real and persistent superstition with no evidence behind it.