I was thinking if the meaning of Poseidon (*Potidahon, *Poseidahon) would be the same as his epithets Enosikhthon, Ennosigaios, Seisikhthon, all meaning "Earth-Shaker". Potidahon would be a Para-Greek adstratal IE word. If we assume that ge:/da: as derivatives of older *gda: / *dga: < *dHg^Hom-, *poti- would mean "shaker" in this Para-Greek language.
I'd like know your comments.
JS Lopes