Why does triskaidekaphopia exist?

Can you turn to the person next to you, look them in the eye, and honestly say that you have never felt a twinge of concern in the morning when you realize it is Friday the 13th? It’s time for triskaidekaphobes to acknowledge their shared superstition, learn its possible source, and try to gain some insight into what it means for millions of people to hold such a belief.
Let’s start with Friday, named for one of two Norse goddesses, Freya or Frigga. While modern folks may exclaim “TGIF,” some traditions consider “Frigga’s Day” to be unlucky. Some Christians aren’t fond of today because they believe Jesus was crucified on a Friday.

Many cultures have an issue with 13, though we can’t say for certain just how many architects actually omit a 13th floor from a highrise. The precise circumstances that made Friday and 13 such an intense combination for superstition are unclear, but a study speculates that businesses lose millions of dollars in revenue from phobias of the day. Some possible origins revolve around the Battle of Hastings, the Knights Templar, or the goddess Frigga once again.
Whatever the source, it’s certain that, however much we want to believe that rationality informs our decisions, logical and systematic thought has limits. For further proof, simply spend some time with a dictionary. Inconsistencies, contradictions and uncertain origins abound.

Activity: What are some other examples of superstition in contemporary life? Saying gesundheit when someone sneezes is certainly one famous word-based example, but what are a few less obvious situations that you’ve experienced?