The exact origins of the phobia are unknown, but some credit Norse mythology for the fear. According to the legend, 12 gods were at a banquet when an uninvited demi god of mischief appeared, bringing the total number of gods to 13. His arrival brought about chaos which led to the death of another god, and the rest of the gods went into mourning.
Thirteen has been an unlucky number since at least 1700 BC, when ancient Babylonia omitted the number 13 in its list of laws. Its association with Friday is a more recent phenomenon.
In 1980, Paramount Pictures released Friday the 13th (tagline: "Fridays will never be the same again"), a slasher flick about a series of murders at a summer camp. Apparently Jason, born on Friday the 13th, chooses that date to take revenge on oversexed campers much like the ones who allowed him to drown in Crystal Lake. So much for trust falls and lanyard-making.
Friday the 13th grossed almost $40 million at the box office and inspired a long-running franchise: Friday the 13th Part II; Friday the 13th Part III; Friday the 13th: The Final Chapter (it was not); Friday the 13th: Jason Lives; Friday the 13th: The New Blood; Friday the 13th: Jason Takes Manhattan (he left the summer camp?); Jason Goes to Hell: The Final Friday; Jason X; and 2003's Freddy vs. Jason.
At the time, Oct. 13, 1989, was the second largest drop of the Dow in history. Nicknamed the Friday-the-13th mini-crash, these days it's not even in the top 10. That might be the scariest fact of all.
5. Three in 2012
2012 has three Friday the 13ths which fall on January, April and July. So after today it's clear sailing for the remainder of the year.