History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
and, as it seems to me, the whole of it had not as yet even this name; nay, before the time of Hellen, the son of Deucalion, it does not appear that this appellation existed at all; but that in their different tribes, and the Pelasgian to the greatest extent, they furnished from themselves the name [of their people.] [*]( i. e. there were different tribes, of which the Pelasgian was the predominant one, called by their different names, instead of being all comprehended under one, as they were afterwards. Or it may refer to the gradual formation of such general names even at that early period, by one tribe extending its own appellation to others.) But when Hellen and his sons had grown strong in Phthiotis, and men invited them for their aid into the other cities; from associating with them, separate communities were now more commonly called Hellenes: [*]( For a striking instance of such a change in the language of a barbarian people at a much later period, I may refer to the inhabitants of the Amphilochian Argos, of whom Thucydides says, II. 68, ἑλληνίσθησαν τὴν νῦν γλῶσσαν τότε πρῶτον ἀπὸ τῶν αμπρακιωτῶν ξυνοικησάντων: οἱ δὲ ἄλλοι ʼαμφίλοχοι βάρ́βαροί εἰσιν.) and yet not for a long time after could that name prevail amongst them all.