Originally Posted by Watcher
As pointed out above, many called others from a different culture "barbarian". Both the Greeks and Persians called each other barbarians.
The Greeks called the Persians barbarians. However, the Persians didn't call the Greeks barbarians.
The word was invented by the Greeks and later used by the Romans. The Graeco-Roman city state culture called barbarians all the other cultures in the world that were not Graeco-Roman and indeed they considered all non-Graeco-Roman cultures to have been "barbaric" (i.e. more primitive), less advanced and inferior. That includes the whole Persian Empire except the Ionian cities briefly under Persian control.
Thucydides for instance, claimed that conditions in Greece several centuries previously, when Hellenic civilization was beginning to emerge, were similar to the conditions in the rest of the world (i.e. the barbarian world).
Barbarians to history fanboys today means that Celtic and Germanic tribes of Northern Europe.