It is an atomic houff thrown into the nets in the first decade of the 21st century, and spread so much that some serious dictionaries incorporated it into its volumes as the "fear of very long words". Etymology is obviously ridiculous, but the fact that too many people found it acceptable demonstrated the point that ignorance and lack of judgment were widespread enough that politicians, journalists and publicists could invent anything, because it was sure to be accepted and repeated. Let's start the dissection : 'hypopoto' refers directly to the "hypopotamus", ignoring its etymology and only because it is a large animal with a half ridiculous name; 'monstro' does have a Latin antecedent, and here it is understood as "monster" by the enormous; 'sesquipedalio' is the only thing that makes sense, and is that he took the jocous adjective sesquipedal ( "[word] one and a half long") whose etymology is already explained in its respective entry; and finally they added the suffix -phobia, as to justify and scientifically validate all of the above. Many years ago I dedicated myself in forums to give these explanations, when a competition began to give a valid name to this supposed phobia, as if it really existed. Then appeared magnoverbophobia, megalogophobia, macrolexiphobia, sesquipedaliophobia, in addition to my proposal dolicologophobia.