Complex sentence: The Locrians around Thermopylae were the first to have been called "Hellenes" and later the name expanded to the other Greek tribes through the Amphictionia of Delphi, to which they belonged, and their religion.
Split into simpler sentences: The Locrians around Thermopylae were the first to have been called "Hellenes". Later the name expanded to include the other Greek tribes through the Amphictionia of Delphi, to which they belonged, and their religion.