Heptadecaphobia

Triskaidekaphobia (pronunciation: /ˌtrɪskaɪˌdɛkəˈfoʊbiə, ˌtrɪskə-/, TRIS-kye-DEK-ə-FOH-bee-ə or TRIS-kə-DEK-ə-FOH-bee-ə; from Greek tris meaning "three", kai meaning "and", deka meaning "10" and phobos meaning "fear" or "morbid fear") is fear or avoidance of the number 13. It is also a reason for the fear of Friday the 13th, called paraskevidekatriaphobia (from Παρασκευή Paraskevi, Greek for Friday) or friggatriskaidekaphobia (after Frigg, the Norse goddess after whom Friday is named in English).