It is estimated that as many as 20 million Americans suffer from a fear of Friday the 13th. The belief in many parts of the Western world that Friday the 13th is the unluckiest day in the calendar is probably the most widespread of all superstitions. The superstition is often said to have ancient origins, and there is a long history of Fridays being unlucky, and the number thirteen as unlucky. But there is no evidence that the combination of the two as Friday the 13th was believed to be unlucky until the late 1800s
Read more about it from Chambers Dictionary of the Unexplained, available online full text through the WSU Library’s subscription to Credo Reference.