Hippopotomonstrosesquippedaliophobia
/ˌhɪ.pəˌpɒ.tə(ʊ)ˈmɒn.stɹə(ʊ)ˌsɛs.kwɪ.pɪˌdɑːl.ɪ.ə(ʊ)ˈfəʊ.bɪ.ə/

(Noun) the fear of seeing, reading, or pronouncing big words.

Usage: The psychiatrist diagnosed her with hippopotomonstrosesquippedaliophobia.

And Rainbow Dash has it. Surely long words don't come about very often right?
...
Right?