Triskaidekaphobia is the fear of 13,  a number commonly associated with bad luck in Western culture. While fear of the number 13 can be traced back to medieval times, the word triskaidekaphobia itself is of recent vintage, having been first coined by Coriat (1911; Simpson and Weiner 1992). It seems to have first appeared in the general media in a Nov. 8, 1953 New York Times article covering discussions of a United Nations committee.

Triskaidekaphobia also may be related to Norse mythology, which tells how the god Odin invited eleven of his closest friends to a dinner party at his home in Valhalla, only to have his party crashed by Loki, the god of evil and turmoil, thus giving a total of 13 people. The legend further relates how Balder, one of the most beloved gods, tried to throw Loki out of the party, resulting in a scuffle and ultimately Balder’s death with a mistletoe-tipped arrow.

Fear of the number 13 also leads to fear of Friday the thirteenth (a fear recently dubbed paraskevidekatriaphobia), despite the fact that Friday turns out to be the most common weekday on which the 13th of a month can occur in the Gregorian calendar. The association of bad luck with Friday appeared in Chaucer’s Canterbury Tales in the late 14th century (“and on a Friday fell all this misfortune”), but references to Friday as a day associated with ill luck in general first appear around the middle of the 17th century (Mikkelson and Mikkelson). In particular, it appeared in numerous publications as a particularly unlucky day to start a new venture (beginning a journey, giving birth, getting married, moving, starting a new job, etc.) beginning around 1800 (Mikkelson and Mikkelson).

source: MathWorld

Norse god Odin – the father of all Norse gods