Friday the 13th: 13 Facts About the Unluckiest Day in the Calendar
"...the fear is real. So real that one scientific name wasn't enough. The fear of Friday the 13th is also called friggatriskaidekaphobia or paraskevidekatriaphobia."
Friggatriskaidekaphobia comes from Frigg, the Norse goddess of wisdom after whom Friday is named, and the Greek words triskaideka, meaning 13, and phobia, meaning fear. Paraskevidekatriaphobia is also derived from Greek: paraskevĂ translates as Friday, and dekatria is another way of saying 13. "
"Experts say that friggatriskaidekaphobia affects millions of people and estimate that businesses, especially airlines suffer from severe losses on Friday the 13th."