Well, it was midnight. I'm responding now.
Calling the Celts barbarians is hardly accurate. Probably the Mongols too, but I don't know much about them.
The Gauls introduced soap to the Romans and Greeks. The "Roman" gladius was a Celtiberian invention.
I'm just a bit sick of people making blanket statements.
Barbarian=tribal. No offense to the Celts intended. The Mongols were tribal until their states became settled too (I would not call either the Yuan Dynasty or the Ilkhanids "barbarians"...but settled peoples with a "barbarian" overlordship leading them).
Perhaps the term "Barbarian" is loaded itself. But we are a bit far removed from then to be hurt by the label, aren't we? I mean...if we decide the Celts were not "barbarians" because we don't like the term...what do you propose as better to differentiate them from, say, Rome, or the Successor states or carthage?