History of Mongolia
Although the Xiongnu finally had been split into two parts in AD 48, the Xianbei (or Hsien-pei in Wade–Giles) had moved (apparently from the east) into the region vacated by the Xiongnu. The Xianbei were the northern branch of the Donghu (or Tung Hu, the Eastern Hu), a proto-Mongol group mentioned in Chinese histories as existing as early as the 4th century BC. The language of the Donghu is believed to be proto-Mongolic to modern scholars. The Donghu were among the first peoples conquered by the Xiongnu. Once the Xiongnu state weakened, however, the Donghu rebelled. By the 1st century AD, two major subdivisions of the Donghu had developed: the proto-Mongolic Xianbei in the north and the Wuhuan in the south.
Ordos culture
In Chinese accounts, the Xiongnu first appear at Ordos in the "Yi Zhou Shu" and "Classic of Mountains and Seas" during the Warring States period before it was occupied by the states of Qin and Zhao. It is generally thought to be their homeland; however, when exactly they came to occupy the region is unclear and archaeological finds suggest it might have been much earlier than traditionally thought.