Wikipedia has more on Heptadekaphobia.
Heptadekaphobia (from the Ancient Greek hepta meaning "seven", and deka meaning "ten", since 7+10=17), Heptakaidekaphobia, or Septadecaphobia is fear of the number 17. the fear may have originated from Italy, where 17 is considered the unlucky number. Italy is also where the roman numeral was patented, which the roman numeral for 17 is XVII, which anagrammically translates to VIXI, which is the Latin word for "I have lived", which in the perfect sense means "my life is over". the fear can also be originated from mythology where Osiris died on the 17th. these imply that the number 17 may believably be a death number. There are some personal causes of Heptadekaphobia, including frequently having horrible days on the 17th, e.g. having really bad day on January 17, then February 17, and so on. some sufferers would have their fears enhanced when full moon occurred on the 17th, which the legend goes back to the death of Osiris during the full moon. few other sufferers may only fear the full moon falling on the 17th, which will next occur in January 2022, which would be the subtractive Mestoselenophobia, Heptadekaphobia hybrid, meaning those sufferers would only fear the full moon when falling on the 17th while only fearing the number when full moon falls on it.
- Heptadekaphobia was mentioned in one of the Jeopardy! clues on July 29, 2014.
- The unluckiness of the number 17 may not be that surprising as it is the sum of 4 (the unlucky number in several Asian countries including China and Japan) and 13 (the unlucky number over much of the world).