[Linked Image from i.imgur.com]

Barbarians can come from all over Faerun, literally all over. There are a couple of places that are famous for Barbarians, such as the tribes of Uthgardt in the northern areas, the Rasheman Berserkers far to the east near Thay, and the tribes from Chondalwood in Chult to the far south.

But a Barbarian isn't just an uncivilised warrior. Barbarians are part of a group that was previously known as the Primal classes, which included Druid, Shaman, Warden, and others that didn't make it into 5e. Primal classes are usually classes that are in some way focused on "primal" energy, being the energy of nature and the natural world, and each class channels this energy in a different way. Different Barbarians channel energy in very different ways too, a Totem Barbarian draws on animal aspects to strengthen them via a totem, an Ancestral Guardian Barbarian draws on the spirits of their ancestors to aid them in battle, etc.

All Barbarians, regardless of where they come from or how they fight are united by their ability to channel their violent urges into a primal rage, that's it really. You don't have to be a naked feral man living rough and eating bugs to be a Barbarian, just embrace the wild rage inside you (see above image). You might have lived in the city, but also spent a lot of time out on the road or in the wilds for various reasons, or maybe you don't actually spend a lot of time out in the wilds, but you've learned to channel your primal rage anyway.