You might suffer from hippopotomonstrosesquipedaliophobia, or fear of long words, if you break out in a cold sweat just thinking about having to read a five-syllable word out loud.
This unusual word is part name of a fear, part mean joke. A shorter word for the same fear is sesquipedaliaphobia, which is already pretty long. The longer version adds a piece derived from the word hippopotamus, which is a long word and a big animal, and a piece derived from monstrum, the Latin word for "monster," which can mean "something very large." Those extra pieces are just there to make the word even longer and add strength to its meaning.