1. Triskaidekaphobia is real – and millions of people have it. It’s not just a word that will win you all the points in Scrabble. Triskaidekaphobia is an irrational fear of the number 13, and if there’s one day when triskaidekaphobia runs rampant, it’s Friday the 13th. While the idea of being afraid of a day might seem silly to some, an estimated 10% of the U.S. population has a fear of the number 13, according to History.com. Oh, by the way, fear of Friday the 13th has its own name: paraskevidekatriaphobia.