A usual wordwide misconception is the association of the word 'Barbarian' with non-Greeks. We all know for starters Epirotes being classed as 'barbarians' from Thucydides, although they were greek-speakers. However the ultimate proof of Greek tribes being called 'barbarians is coming from Athenaios Deipnosophistes where Stratonicus the harp-player was asked "πότερα Βοιωτοί βαρβαρώτεροι...ή θετταλοί, Ηλείους έφησεν" meaning ...

 (Herodotus 5.22)   XXII. Now that these descendants of Perdiccas are Greeks, AS THEY THEMSELVES SAY, I MYSELF CHANCE TO KNOW AND WILL PROVE IT in the later part of my history. Furthermore, the Hellenodicae who manage the contest at Olympia determined that it is so, [2] for when Alexander chose to contend and entered the lists ...