Getting hung up on the original sense of the wording, or the original meaning of the word is the main mistake here, and you'll probably have a better time of things if you don't do that. Think of it this way, as a similar analogy:
"When I think of 'Orcs', I think of (Orcs as defined by Lord of the Rings), so I'm really not sure how to rp them like that in this Faerunean setting where (origin of tolkien orcs) does not exist!" - the answer is, *Don't*. Tolkien orcs and Forgotten Realms orcs are not the same, and they're two completely different things - they may share some mythological origin roots, but they are, in the present day, completely unrelated to one another and it makes no sense at all to even think of one as the other.
The same is true of Barbarians - FR Barbarians plain and simply are *not* "primitive tribal warriors". They *can* be - a primitive tribal warrior can certain be a barbarian - but that is not the definition of a barbarian, and it makes no sense to treat one as the other. They simply aren't the same. Treat the word barbarian, as used in the realms, as a homonym to your real-world conception of barbarians, nothing more. Piff's description is actually a pretty good summary of what lies at the core of FR barbarians.
