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.
Origin of the Huns
There are, however, potential problems with equating the names "Xiōngnú" and "Hun". Maenchen-Helfen notes that the Chinese transcription is only an approximation of their actual name. As proof of its imprecision, he notes that Emperor Wang Mang actually renamed the Xiongnu as the Hsiang-nu, with the first element meaning "to submit", while on bad terms with the group. Later, when on good terms, he renamed them Kung-nu, with the first element meaning "respectful". Christopher Beckwith, moreover, notes that the pronunciation of Xiongnu in Old Chinese is uncertain. While it was likely pronounced "*χoŋnʊ" or "*χʲoŋnʊ" in Middle Chinese, it is possible it was taken into Old Chinese before the change of initial "s" to "χ", meaning it could correspond to an Iranian name like Saka or "skuδa" (Scythian). E.G. Pulleyblank suggested an Old Chinese pronunciation similar to "*flông-nah" and connected this name to a nomadic people attested in Greek as the Phrounoi ("Φροῦνοι").