A bit of useless info: The (Greek) term "paraskevidekatriaphobia" is a much later one, inelegantly cobbled together. The original, ancient Greek term, is "triskedekaphobia" (rolls off the tongue easier too), meaning simply "fear of thirteen".

"Paraskevi" (Friday)is a much later addition, in Christian times, and simply hooks up the superstition of the number thirteen with the Good Friday element (Christ's crucifixion). In Greece it is Tuesday that has become linked with it instead, commemorating the fall of Konstantinople and the ending of the Byzantine empire oon Tuesday 13th May 1453.

But triskedekaphobia is much, much older than that. Though many attempt to reason its existence based on latter-day elements (thirteen sat down to eat at the Last Supper, etc etc), the term and its origins are lost in the distant undocumented past.

There - you're all much better informed now!