This tongue twister was coined by Coriat (1911; Simpson and Weiner 1992). The fear of the number thirteen has led to some strange numerical decisions- many high-rise hotels don’t have a thirteenth floor. The idea of 13 as evil has been associated with the 13 people present during the Last Supper. The fear of Friday the thirteenth is called dubbed paraskevidekatriaphobia.
Here’s an example of how Stephen King explained Triskaidekaphobia without mentioning it:
“There were fourteen steps exactly fourteen. But the top one was smaller, out of proportion, as if it had been added to avoid the evil number.”