Some believe that the arrest of Jacques de Molay, Grand Master of the Knights Templar, and 60 of his senior knights on Friday, October 13, 1307 by King Philip IV of France is the origin of this superstition. That day thousands of Templars were arrested and subsequently tortured. They then ‘confessed’ and were executed. From that day on, Friday the 13th was considered by followers of the Templars as an evil and unlucky day.
Image: Jacques de Molay sentenced to the stake in 1314, from the Chronicle of France or of St Denis (fourteenth century). Note the shape of the island, representing the Île de la Cité (Island of the City) in the Seine where the executions took place.