The phobia of Friday the 13th is called paraskevidekatriaphobia or friggatriskaidekaphobia. Paraskevidekatriaphobia is an acute and irrational fear of Friday the 13th, and it is an extension of triskaidekaphobia, which is a phobia of the number 13. The term paraskevidekatriaphobia comes from the Greek words "paraskeví" meaning Friday, "dekatreís" meaning thirteen, and "phóbos" meaning fear. Friggatriskaidekaphobia is another name given to the fear of Friday the 13th, and it comes from Old Norse "Frigg" meaning Frigg, Ancient Greek "treiskaídeka" meaning thirteen, and "phóbos" meaning fear.