Ordos Plateau
In Chinese accounts, the Xiongnu first appear at Ordos in the "Yizhoushu" and "Shanhaijing" during the Warring States period before it was occupied by Qin and Zhao. It is generally thought to be their homeland, however when exactly they came to occupy the region is unclear, and it might have been much earlier than traditionally thought, as suggested by archaeological finds. As the Xiongnu expanded southward into Yuezhi territory around 160 BC under their leader Modun, the Yuezhi in turn defeated the Sakas (Scythians) and pushed them away at the Issyk Kul. It is thought the Xiongnu also occupied the Ordos area during the same period, when they came in direct contact with the Chinese. From there, the Xiongnu conducted numerous devastating raids into Chinese territory (167, 158, 142, 129 BC). The Han Dynasty started to fight the Xiongnu in the 2nd century BC under emperor Han Wudi, and colonized the area of the Ordos under Shuofang commandery in 127 BC. Prior to the campaign, there were already commanderies established earlier by Qin and Zhao until they were overrun by the Xiongnu in 209 BC.
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").