The origin of Friday the 13th being an “unlucky day” goes back to the days of the Knights Templar. On September 12th, 1307 King Philip of France sent sealed letters to his governors and officials to arm themselves on the 12th of the next month and open the sealed orders and act upon them. By the morning of Friday, October 13th almost every Templar in France was in the King’s custody, thus Friday the 13th being an unlucky day. This was also the first “October surprise” as no one had seen this coming.
The Knight’s Templar back then were accused by the Pope of being heretics and worshiping the devil, and today many conspiracy theorist hold that they were the beginning of what would become the “Illuminati”. However, they were actually an Order that while starting out as a group of Catholic Knights, they ended up becoming the custodians and protectors of an Ancient Esoteric tradition that they had learned from the Moors.
While thought to have been disbanded after October 13th, 1307, both the Knights Templar Order and the Esoteric Tradition they held survived and would later reemerge in history within the Rosicrucian Order and the Freemasons.