Occasionally it'll take the form friggatriskaidekaphobia, but that's rarer. Here, we analyze the term paraskavedekatriaphobia, or "the fear of Friday the 13th". The first element, paraskavei, is the Greek term for "Friday" and in Ancient Greek literally meant "day of preparation" as paraskeue. This in turn is a portmanteau of para-, meaning "half", and skeue, meaning "dress". After all, while you're preparing, you're only half-dressed. The second element, dekatreis, is Greek for "thirteen", and is composed of deka-, or "ten" (from Proto-Indo-European dekm, which may be connected to komt, "hand"), and tris, or "three" (also PIE). Finally, phobia is from phobos ("fear"), from phebomai ("to flee"; makes sense), from PIE bhegw, "to run". So, what today means "fear of Friday the Thirteenth" can be broken up into five Greek words meanining "half-dressed three-hand running"!
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd