Frig!

The fear of Friday the 13th is called friggatriskaidekaphobia, frigga, meaning "Friday" and triskaidekaphobia, or paraskevidekatriaphobia, a word derived from the concatenation of the Greek words Paraskeví (Παρασκευή, meaning "Friday"), and dekatreís (δεκατρείς, meaning "thirteen"), attached to phobía (φοβία, from phóbos, φόβος, meaning "fear"). The word was derived in 1911 and first appeared in a mainstream source in 1953.