Did you know that triskaidekaphobia is the irrational fear of the number 13? Or that triskaidekaphobia is so wide spread that the Otis Elevator Company does not even include a button with a 13 on it in elevators all over the world. Or that Triskaidekaphobes have assigned the number 13 as the reason for explosion of Apollo 13, which took off at exactly 1:13 p.m. (1313 military time) on 4/11/70 (digits that add up to 13, naturally). Freaky!!!
To ancient Egyptians, whose quest for spiritual ascension unfolded in 13 stages (twelve in this life and one beyond), the number 13 symbolized death. But, they didn't see death as the end. They believed death was a glorious and desirable transition into an eternal life. And while the ancient Egyptian civilization perished we could assume the symbolism conferred on the number 13 by its priesthood survived only to be corrupted by subsequent cultures who came to associate 13 with a fear of death instead of a reverence for the afterlife.
The number 13 was also revered in the prehistoric goddess worshiping cultures, because it corresponded to the number of lunar (menstrual) cycles in a year (13 x 28 = 364 days). But with the rise of male-dominated civilization, the solar calendar triumphed over the lunar, and the "perfect" number 12 triumphed over the "imperfect" number 13, which then became a number of fear and loathing.
Now about Friday.
The name "Friday" was derived from a Norse deity worshiped on the sixth day, known either as Frigg (goddess of marriage and fertility), or Freya (goddess of sex and fertility), or both. Frigg/Freya corresponded to the Roman goddess of love Venus. The Romans named the sixth day of the week "dies Veneris." to honor their goddess.
Friday was actually considered quite lucky by the pre-Christian Teutonic peoples, and because of its association with love and fertility was considered an especially good day to get married.
However, pagan practices were not looked on with favor by the Church, which went to great lengths to suppress them, And, and during the Middle Ages Friday became known as the "Witches' Sabbath." And Freja, the goddess of the sixth day, whose sacred animal was the cat, was recast as a witch, and her day became associated with evil doings.
Friday's bad reputation could go all the way back to the Gensis's Garden of Eden. Supposedly, it was on a Friday, that Eve became the first temptress when she persuaded Adam to taste the forbidden fruit... which resulted in both being expelled from Paradise.
Biblical tradition also holds that the Great Flood began on a Friday, that God tongue-tied the builders of the Tower of Babel on a Friday, that the Temple of Solomon was destroyed on a Friday and Friday is also said to be the day of the week on which Christ was crucified. Friday was execution day in pagan Rome and later became Hangman's Day in Britain. In other pre-Christian cultures Friday was the sabbath, a day of worship and to receive the blessings of the gods.
So there you have it... unlucky Friday + unlucky 13 = unluckier Friday