Paraskevidekatriaphobia

That is the official name for fear of Friday the 13th. Therapist Dr. Donald Dossey, whose specialty is treating people with irrational fears, coined the term paraskevidekatriaphobia. Another is known as friggatriskaidekaphobia. The fear of the day is likely rooted in Christianity. Jesus was crucified on a Friday and ever since the day has been associated with general ill omen according to Michael Bailey, a history professor at Iowa State University who specializes in the origins of superstitions. See also LINK

Weddings in the Middle Ages were not held on Fridays and it was not a day someone would start a journey. Thirteen guests are believed to have attended the Last Supper, the night before Jesus was killed, according to Stuart Vyse, a psychology professor at Connecticut College. Judas Iscariot, the disciple who betrayed Jesus, is considered to have been the 13th guest, Vyse said.

It is unclear when Friday and number 13 became linked in the way we think of them today, according to Vyse and Bailey. There are no mentions of Friday the 13th before the 19th century.

Taylor Swift says her lucky number is 13. "I was born on the 13th. I turned 13 on Friday the 13th. My first album went gold in 13 weeks. My first #1 song had a 13-second intro." The performer was sued in 2014 by the clothing brand Lucky 13 for selling T-shirts on her online store with the phrase "Lucky 13" on them.