As presented in OA and UA 1st edition, barbarians, the character class, came from three distinct areas: tundra, grasslands, and jungle. Given the focus that TSR had at the time on pushing Oriental Adventures and its related products, it seems clear to me that their underlying thoughts were that these correspond broadly to Siberia, Mongolia/Xinjiang, and Indochina/Bengal. WotC has of course broadened the concept since then, but at the time, TSR had some serious orientalism going on. It's worth noting that the barbarian class in that edition did not have the rage class feature.
The 1e Unearthed Arcana barbarian which predated Oriental Adventures (and in turn was based on a Dragon article I believe) was very much not orientalist in that way. It seemed based on Conan and then applied straight to Norse/Germanic types; Huns, Mongols, and other steppe nomads with some horse stuff; and to people from jungle areas like the amazon with stuff like blowguns and such and did not say people from the orient are barbarians while westerners are civilized.
The art accompanying the class certainly does not suggest barbarians are primarily Asian.
It explicitly says:
Native territory: Many of a barbarian’s abilities depend on the native territory of the character. It is mandatory that barbarian characters come from some out-of-the-way barbaric state or area within the campaign. Typically they are cavemen, dervishes, nomads, or tribesmen. Only such uncivilized backgrounds can generate the necessary surroundings to produce individuals of the stock from which barbarian fighters would be drawn.
Within the WORLD OF GREYHAWK” Fantasy Game Setting, for example, there are several areas that could spawn the barbarian subclass.
The lands of the Frost, Ice, and Snow Barbarians, as well as the Hold of Stonefist, would be the homeland of
barbarians of the Scandinavian/Slavic mold. These characters would employ broad swords and short bows in addition to the required initial weapons. Horsemanship would be nominal at best, but these barbarians would have running abilities and the skill in small craft, rowed.
Barbarians from the Rovers of the Barrens, Tiger, and Wolf Nomads would be excellent horsemen. The Rovers, being the most barbaric of these groups, would have the tertiary abilities of running, animal handling, paddled small craft, sound imitation, and snare building. Their main weapons would be the club, javelin, and lasso or short bow. Other Nomads from this group would be most efficient at long distance signaling, and skilled in the use of the lance, scimitar, and composite short bow.
Savages of the Amedio Jungle or Hepmonaland would have the tertiary abilities of long distance signaling, running, sound imitation, snare building, and possibly paddled small craft. In the Amedio Jungle, the preferred weapons would be club, blowgun or shortbow, and dart or javelin. In Hepmonaland, the typical weapons would be atlatl and javelin, club, and short sword.
Using the above as examples, the DM can tailor his barbarians to fit his campaign. Not only does the native area determine initial weapons known, but it also serves as a base of judgment for the use of secondary abilities. These abilities are severely limited outside the native territory of the barbarian, until the character becomes more effective with his or her abilities by gaining familiarity with the new area.
For OA and the Oriental Barbarian it says:
Within the world of Oriental AD&D® Adventures, there are three territories where barbarians live—the barren steppelands, the forested seacoasts of the north, and the jungles of the south. All barbarians come from one of these areas. Each area allows the character a different selection of proficiencies.
Steppeland barbarians: These barbarians are roving nomads, masters of the horse. Their preferred weapons are the light lance, horsebow, sword, and hand axe. Proficiencies they can choose from are horsemanship, long-distance signaling, outdoor craft, tracking, animal handling, weapon smith, armorer, bowyer, running, dancing, singing, weaving, tanning, sound imitation, survival, and chanting. These barbarians usually live in leather tents, following the movements of migratory herds. They raise small herds of cattle and sheep, but practice no other agriculture.
Forest barbarians: These barbarians live in the snowy forests that dot small islands and line the coasts of the northern part of the world. Their preferred weapons are spear, shortbow, hand axe, harpoon, and sword. Proficiencies they can choose from are small water craft, fishing, tracking, survival, animal handling, weapon smithing, pottery, bowyer, sound imitation, snare building, weaving, tanning, carpentry, agriculture, singing, chanting, dancing, and rhetoric. These barbarians live in small, permanent villages. The women raise small crops, the men hunt and fish.
Jungle barbarians: These people live in the tropical jungles of the south. Their preferred weapons are blowgun, spear, sword, hand axe, and dagger. Proficiencies they can choose from are small water craft, fishing, swimming, survival, animal handling, carpentry, weapon smith, armorer, sound imitation, snare building, pottery, tracking, chanting, dancing, music, and sailing craft. They live in permanent villages, surviving by gathering jungle plants, hunting wild animals, and fishing.
