"Triskaidekaphobia"-say that five times fast

There were 13 people at the Last Supper, one of whom betrayed Jesus, as well as Jesus being crucified on a Friday.

In Leonardo da Vinci's The Last Supper, the figure at Jesus' right arm does not possess an easily identified gender. ... Is the Figure Mary Magdalene?

Fact: Mary Magdalene wasn't listed among those at the table in any of the four Gospels.

Yes, she was present during the Last Supper, according to Biblical accounts. Her role, however, was a minor supporting one. She wiped feet.

Chronicling their fascinating quest for truth through time and space, the authors reveal an astonishing new view of the real motives and character of the founder of Christianity, as well as the actual historical -- and revelatory -- roles of John the Baptist and Mary Magdalene.

Is pop culture to blame? (or)...Are there origins in religion?
While definite origins of the Friday the 13th superstition are unknown, many articles and research papers point to Christianity. Thirteen people attended the Last Supper: 12 disciples and Jesus. The following day — a Friday — Jesus was killed, Baldauff said.

Not everyone is convinced of religious ties, however. Luft said while fears of the number 13 and Friday are common in America, nothing in the Bible suggests aversions to either during the years the book covers or the centuries following.

Friday the 13th superstitions are rooted in ancient bad-luck associations with the number 13 and the day Friday, said Donald Dossey, a folklore historian and author of Holiday Folklore, Phobias and Fun.

The two unlucky entities ultimately combined to make one superunlucky day. Dossey traces the fear of the number 13—aka, triskaidekaphobia—to a Norse myth about 12 gods having a dinner party at Valhalla, Norse mythology's heaven. In walked the uninvited 13th guest, the mischievous god Loki. Once there, Loki arranged for Hoder, the blind god of darkness, to shoot Balder the Beautiful, the god of joy and gladness, with a mistletoe-tipped arrow. "Balder died, and the whole Earth got dark. The whole Earth mourned. It was a bad, unlucky day," Dossey said.

There is also a biblical reference to the unlucky number 13. Judas, the apostle said to have betrayed Jesus, was the 13th guest to the Last Supper. (See "Lost Gospel Revealed; Says Jesus Asked Judas to Betray Him.") As for Friday, it's well known among Christians as the day Jesus was crucified.

Jane Risen, a behavioral scientist at the University of Chicago Booth School of Business, has found that superstitions can influence even nonbelievers. In one study, Risen found that people who identify as superstitious and non-superstitious both believe a bad outcome is more likely when they've been jinxed, such as by stating they definitely won't get into a car accident.
“Generally speaking, I find that this occurs because the bad outcome springs to mind and is imagined more clearly following the jinx,” she explains. “People use the ease of imagining something as a cue to its likelihood.”

Jane L. Risen conducts research in the areas of judgment and decision making, intuitive belief formation, magical thinking, stereotyping and prejudice, and managing emotion.

Rooted in Religion?
Where does a fear of Friday the 13th come from in the first place?

It's difficult to pin down the origins and evolution of a superstition. But Stuart Vyse, a professor of psychology at Connecticut College in New London, said our fear of Friday the 13th may be rooted in religious beliefs surrounding the 13th guest at the Last Supper—Judas, the apostle said to have betrayed Jesus—and the crucifixion of Jesus on a Friday, which was known as hangman's day.