History of the Peloponnesian War (1.3.1-1.3.3)

The weakness of the olden times is further proved to me chiefly by this circumstance, that before the Trojan war, Hellas, as it appears, engaged in no enterprise in common.

Indeed, it seems to me that as a whole it did not yet have this name, either, but that before the time of Hellen, son of Deucalion, this title did not even exist, and that the several tribes, the Pelasgian most extensively, gave their own names to the several districts; but when Hellen and his sons became strong in Phthiotis and were called in to the aid of the other cities, the clans thenceforth came more and more, by reason of this intercourse, to be called Hellenes, though it was a long time before the name could prevail among them all. The best evidence of this is given by Homer;

for, though his time was much later even than the Trojan war, he nowhere uses this name of all, or indeed of any of them except the followers of Achilles of Phthiotis, who were in fact the first Hellenes, but designates them in his poems as Danaans and Argives and Achaeans. And he has not used the term Barbarians, either, for the reason, as it seems to me, that the Hellenes on their part had not yet been separated off so as to acquire one common name by way of contrast.