It is most likely that it was named after the Homeric Ermioni.

Ermioni dates back to the 2nd century according to Pafsanias. There existed many temples and sanctuaries, dedicated especially to goddesses. The most significant, that of the chthonic Demeter, was a holy sanctuary. Behind that, was the location of Klymenus, with an earth gap from where Hercules brought Cerberus from Hades, the underworld.

The Turks couldn't stay firm in this area - because of its rough passage. In this manner Ermioni maintained her Greek life style without tolerating forreign influences.