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.
Cong (surname)
The Congs are originally of Xiongnu origin. They trace their ancestry to King Xiutu of the Xiongnu. In 121 BC, Xiongnu King Hunxie killed King Xiutu when Xiutu refused to surrender to the Chinese with Hunxie. The fourteen-year-old Crown Prince Midi was taken to China and raised as a stable hand. One day, when Emperor Wu of Han was inspecting the horses with his wives, all the servants were mesmerized by the royal entourage, except for Midi. Emperor Wu of Han took favor of the prince and granted him the Chinese surname Jin, meaning gold, because the prince used to make sacrifices with golden statues as a part of the Xiongnu rituals.