Triskaidekaphobia

Triskaidekaphobia (/ˌtrɪskaɪˌdɛkəˈfoʊbiə/ ^ⓘ TRIS-kye-DEK-ə-FOH-bee-ə, /ˌtrɪskə-/ TRIS-kə-; from Ancient Greek τρεισκαίδεκα (treiskaídeka) 'thirteen' and Ancient Greek φόβος (phóbos) 'fear') is fear or avoidance of the number 13. It is also a reason for the fear of Friday the 13th, called paraskevidekatriaphobia (from Greek Παρασκευή (paraskevi) 'Friday'; Greek δεκατρείς (dekatreís) 'thirteen' and Ancient Greek φόβος (phóbos) 'fear') or friggatriskaidekaphobia (from Old Norse Frigg 'Frigg' and from Ancient Greek τρεισκαίδεκα (treiskaídeka) 'thirteen' and Ancient Greek φόβος (phóbos) 'fear').

The term was used as early as in 1910 by Isador Coriat in Abnormal Psychology.

The supposed unlucky nature of the number 13 has several theories of origin. Although several authors claim it is an older belief, no such evidence has been documented so far. In fact, the earliest attestation of 13 being unlucky is first found after the Middle Ages in Europe.

Tarot card games have been attested since at least around 1450 with the Visconti-Sforza Tarot. One of the trump cards in tarot represents Death, and is numbered 13 in several variants.

In 1781, Antoine Court de Gébelin writes of this card's presence in the Tarot of Marseilles that the number thirteen was "toujours regarde comme malheureux" ("always considered as unlucky"). In 1784, Johann Gottlob Immanuel Breitkopf cites Gébelin, and reaffirms that the tarot card number 13 is death and misfortune ("Der Tod, Unglück").

Since at least 1774, a superstition of "thirteen at a table" has been documented: if 13 people sit at a table, then one of them must die within a year. The origin of the superstition is unclear and various theories of its source have been presented over the years.

In 1774, Johann August Ephraim Götze speculated:

Da ich aus der Erfahrung weis, daß der Aberglaube nichts liebers, als Religionssachen, zu seinen Beweisen macht; so glaube ich bey nahe nicht zu irren, wenn ich den Ursprung des Gegenwärtigen mit der Zahl XIII, von der Stelle des Evangelii herleite, wo der Heiland, bey der Ostermahlzeit, mit zwölf Jüngern zu Tische saß.
Since I know from experience that superstition loves nothing better than religious matters as its proofs, I believe I'm almost certainly unmistaken when I derive the origin of the matter of the number XIII from the passage of the Gospel where the Savior sat at table with twelve disciples at the Easter meal.