Fear of long words. Since 'sesquipedaliaphobia' already means fear of long words, the other part is added on by those with hypopseudoliteratiobfuscationarianism.
"Homer retaliated, triggering Aesop's hippopotomonstrosesquipedaliaphobia with a hypopseudoliteratiobfuscationarionisticism of his own before jumping to a floccinaucinihilipilification of the whole process."
by DC Dave January 29, 2016