Here are some facts about the fear of Friday 13th!
Friday the 13th, 'the most widespread superstition'
The sixth day of the week and the number 13 both have foreboding reputations said to date from ancient times. It seems their inevitable conjunction from one to three times a year (there will be three such occurrences in 2012) portends more misfortune than some credulous minds can bear. According to some sources it's the most widespread superstition in the United States today. Some people refuse to go to work on Friday the 13th; some won't eat in restaurants; many wouldn't think of setting a wedding on the date.
Although no one can say for sure when and why human beings first associated the number 13 with misfortune, the superstition is assumed to be quite old, and there exist any number of theories, one such is primitive man had only his 10 fingers and two feet to represent units, this explanation goes, so he could count no higher than 12. What lay beyond that — 13 — was an impenetrable mystery to our prehistoric forebears, hence an object of superstition.
To the ancient Egyptians, we're told, life was a quest for spiritual ascension which unfolded in stages — twelve in this life and a thirteenth beyond, thought to be the eternal afterlife. The number 13 therefore symbolized death, not in terms of dust and decay but as a glorious and desirable transformation. Though Egyptian civilization perished, the symbolism conferred on the number 13 by its priesthood survived, we may speculate, 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 name "Friday" was derived from a Norse deity worshipped on the sixth day, known either as Frigg (goddess of marriage and fertility), or Freya (goddess of sex and fertility), or both, the two figures having become intertwined in the handing down of myths over time (the etymology of "Friday" has been given both ways). Frigg/Freya corresponded to Venus, the goddess of love of the Romans, who named the sixth day of the week in her honor "dies Veneris."
Friday was actually considered quite lucky by pre-Christian Teutonic peoples, we are told — especially as a day to get married — because of its traditional association with love and fertility. All that changed when Christianity came along. The goddess of the sixth day — most likely Freya in this context, given that the cat was her sacred animal — was recast in post-pagan folklore as a witch, and her day became associated with evil doings.
Various legends developed in that vein, but one is of particular interest: As the story goes, the witches of the north used to observe their sabbath by gathering in a cemetery in the dark of the moon. On one such occasion the Friday goddess, Freya herself, came down from her sanctuary in the mountaintops and appeared before the group, who numbered only 12 at the time, and gave them one of her cats, after which the witches' coven — and, by "tradition," every properly-formed coven since — comprised exactly 13.
For more facts check out theses items in CARL
031 Extraordinary origins of everyday things
1987, ISBN 0060960930, 1st ed., xi, 463 p.
390 How did it begin?: customs & superstitions, and their romantic origins
1966, 1st American ed., xix, 352 p.
394.26973 The folklore of American holidays
1987, ISBN 9780810321267, 1st ed., xxxi, 431 p.
398.303 A brief dictionary of American superstitions
1959, 259 p.