Who's Afraid of Friday the 13th?

Friggatriskaidekaphobics are surely hiding behind closed doors (unless they are claustrophobics too), avoiding black cats, mirrors and salt today.

According to the website The Unexplained Mysteries, the fear of Friday the 13th is called "friggatriskaidekaphobia." Frigga, meaning "Friday," and triskaidekaphobia, or paraskevidekatriaphobia, derived from the Greek words "Paraskevi" (Friday) and "dekatreis" (thirteen). The word reportedly was coined in 1911 and appeared in a mainstream source in 1953, according to the site.

There are many superstititions surrounding the number "13."

In modern numerology, 12 is considered the number of completeness (months of the year, Zodiac, hours, tribes of Israel, Apostles of Jesus, etc.). The number 13 is considered irregular, according to the website.

Superstition also stems from the Christian Last Supper – having 13 people seated at a table will result in the death of one of the diners.

Chaucer's "The Canterbury Tales" regarded Friday as an unlucky day for journeys or new projects. Remember the stock market crash? It occurred on a Friday. Any Christians out there? So you know when Jesus was crucified.

Author Charles Panati traces back the superstition to Norse mythology. Friday is named for Frigga, the goddess of love and fertility. According to The Unexplained Mysteries, when Norse and Germanic tribes converted to Christianity, Frigga was banished in shame to a mountaintop and labeled a witch. It was believed that every Friday, the spiteful goddess convened a meeting with eleven other witches, plus the devil — a gathering of thirteen — and plotted ill turns of fate for the coming week.