Barbaros imitates unintelligible speech, the bar-bar of non-Greek tongues, and appears already in Homer for non-Greek speakers, without savagery attached: the Carians are barbarophonoi, foreign-voiced, not villains. Herodotus applies barbarian broadly to non-Greeks, often respectfully, Persian and Egyptian civilizations included. After the Persian wars the word hardened into a moral line, and Rome inherited it for everyone outside the empire, at times including Greeks.
The pattern as the ancients lived it: Greeks mocked Persian speech, Persians kept their own hierarchies of peoples, Romans despised the northern tribes, and the tribes, Goths, Vandals, walked into Rome and kept the crown. The word's whole history is a wheel: today's babblers are tomorrow's emperors.
The theoretical claim: the word did not describe the foreign, it manufactured the border. Naming speech as noise lets a group treat its own conventions as language itself, and every institution since has had its bar-bar: the accent, the jargon, the uninitiated. Civilization, on this reading, is not a level of development. It is a listening habit.
The word started as an accent gag and ended as a caste system. If civilization is defined by who sounds wrong, whose speech is the punchline right now?