So, what's the deal with Friday the 13th? The superstition seems to relate to various things, like the story of Jesus' last supper and crucifixion in which there were 13 individuals present in the Upper Room on the 13th of Nisan Maundy Thursday, the night before his death on Good Friday. While there is evidence of both Friday and the number 13 being considered unlucky, there is no record of the two items being referred to as especially unlucky in conjunction before the 19th century.
The superstition appears to be related to the extreme tragedy of theTrials of the Knights Templar which started with their arrest in Friday 13 October 1307, which was perpetrated by Philip IV of France and his counselors with aims to acquire the wealth of the Templars.
According to folklore historians, the unlucky nature of the number "13" originated with a Norse myth about 12 gods having a dinner party in Valhalla. The trickster god Loki, who was not invited, arrived as the 13th guest, and arranged for Höðr to shoot Balder with a mistletoe-tipped arrow. "Balder died, and the whole Earth got dark. The whole Earth mourned. It was a bad, unlucky day." This major event in Norse mythology caused the number 13 to be considered unlucky.
It is possible that the publication in 1907 of Thomas Lawson's popular novel Friday, the Thirteenth, contributed to disseminating the superstition. In the novel, an unscrupulous broker takes advantage of the superstition to create a Wall Street panic on a Friday the 13th.