What is the word for the fear of long words?

The word for the fear of long words is hippopotomonstrosesquippedaliophobia.

The term is a humorous, self-referential coinage: it is itself an unusually long word describing anxiety about long words. Its parts draw on Greek and Latin roots, including hippopotamus, monstrum (something monstrous), sesquipedalian (literally “a foot and a half long”), and phobos (fear).

The shorter term sesquipedalophobia is also used, and megalologophobia is another defensible formation from Greek roots meaning “fear of big words.” However, hippopotomonstrosesquippedaliophobia is the familiar trivia answer and the single answer most quizmasters expect. The spelling can vary slightly, including forms with or without an extra “s” in the middle.

It is also worth noting that this label is generally treated as a playful or informal term rather than a standard, independently recognized diagnosis. A genuine fear of words or speaking may instead relate to a specific phobia, social anxiety, or fear of making mistakes when speaking.