"The language criteria of Greekness was vital, since the Greek verb hellenizein, literally 'to be Greek', basically and originally meant to speek Greek. And this for the Macedonians was a problem. There existed an adverb, makedonisti, that ment 'in Macedonian' (the language or dialect), and that betokened the fact that Macedonians could speak among themselves a language or a dialect that was incomprehensible to other, more standard Greek-speakers. And incomprehemsible too, in such a way as to raise the issue of wheather Macedonian speech was fundamentally Greek.
There were some Greek speakers, it is true, whose version of Greek (local idioms and/or thick accent) caused other Greeks to sneer or laugh at them. The Spartans' spoken Greek struck the Athenian that way, for example. But there was no question of thier being thought not Greek -- or not wholly Greek or not Greek enough -- as a result.
This was, however, the case with the Macedonian language. It is therefore quite telling that when another standard test of Greekness was applied to Macedonians -- namely, whether or not they were eligible to compete in the all-Greek and only Greek Olympic Games -- the answer delivered by the authorities (of teh city of Elis) in charge of et hgames was deeply ambivalent. Only the King of the Macedonians, they decreed should be considered eligible -- meaning that the Greek status of the rest of his subjects was left at best in limbo. ..."
(Paul Carteledge, Thermopylae, Vintage Books, A Division of Random House, New York, 2006. Seite 60 und 61)