Fear of Friday the 13^th is called paraskevidekatriaphobia It's an intense or irrational fear of Friday the 13^th - from Greek Παρασκευή (Paraskevi) 'Friday', Greek δεκατρείς (dekatreís) 'thirteen', and Ancient Greek φόβος (phóbos) 'fear'. Fear of Friday the 13^th is also called friggatriskaidekaphobia - from Old Norse Frigg 'Frigg', Ancient Greek τρεισκαίδεκα (treiskaídeka) 'thirteen', and Ancient Greek φόβος (phóbos) 'fear'