According to the book Panati’s extraordinary origins of everyday things by Charles Panati on page 13 (of course), this is the history behind Friday the thirteenth.

Efforts to account for this unluckiest of days have focused on disastrous events alleged to have occurred on it. Tradition has it that several bible stories occurred on Friday the Thirteenth.

The actual origin of the superstition, though, appears also to be a tale in Norse mythology.

Friday is named for Frigga, the free-spirited goddess of love and fertility. When Norse and Germanic tribes converted to Christianity, Frigga was banished in shame to a mountaintop and labeled a witch. It was believed that every Friday, the spiteful goddess convened a meeting with eleven other witches, plus the devil -a gathering of thirteen- and plotted ill turns of fate for the coming week. For many centuries in Scandinavia, Friday was known as “Witches’ Sabbath”.