Triskaidekaphobia

triskaidekaphobia \tris-ky-dek-uh-FOH-bee-uh\, noun:
triskaidekaphobic, adjective and noun; triskaidekaphobe, noun

a morbid fear of the number 13

"Thirteen people, pledged to eliminate triskaidekaphobia, fear of the number 13, today tried to reassure American sufferers by renting a 13 ft plot of land in Brooklyn for 13 cents... a month.''
--Daily Telegraph, January 14, 1967

"A discussion in the U.N. last week on the number of members on a committee raised the question of triskaidekaphobia.''
--New York Times, November 8, 1953

"Past disasters linked to the number 13 hardly help triskaidekaphobics overcome their affliction. The most famous is the Apollo 13 mission, launched on April 11, 1970 (the sum of 4, 11 and 70 equals 85 - which when added together comes to 13), from Pad 39 (three times 13) at 13:13 local time, and struck by an explosion on April 13.''
--"It's just bad luck that the 13th is so often a Friday,'' Electronic Telegraph, September 8, 1996

Triskaidekaphobia is from Greek treiskaideka, triskaideka, thirteen (treis, three + kai, and + deka, ten) + phobos, fear.

In Christian countries the number 13 was considered unlucky because there were 13 persons at the Last Supper of Christ. Fridays are also unlucky, because the Crucifixion was on a Friday. Hence a Friday falling on the thirteenth day is regarded as especially unlucky.

Some famous triskaidekaphobes*:

--Napoleon
--Herbert Hoover
--Mark Twain
--Richard Wagner
--Franklin Roosevelt

* Source: ``It's just bad luck that the 13th is so often a Friday,'' Electronic Telegraph, September 8, 1996

Happy Friday the 13th! ;-)