Triskaidekaphobia  (from  Greek   tris  meaning "3",  kai  meaning "and",  deka  meaning "10" and  phobia  meaning "fear" or "morbid fear") is  fear  of the number  13 ; it is a  superstition  and related to a specific fear of  Friday the 13th , called  paraskevidekatriaphobia  or friggatriskaidekaphobia . .  One time, many