I had never suspected that the Chinese word for “Chinese” has a foreign origin. But yes, it does. In fact, the same foreign word has been borrowed twice and yielded two different Chinese words, one of which is widely used as the ethnonym for “Chinese”.’“At any rate, the same word, or etymologically a homophonous loanword which came to be written with the same character, came to serve as the name of “us, Chinese”. According to Beckwith, in this meaning the term does not predate the Warring States period, the final part of the Zhou age (-5th to -3rd). At that time, knowledge was extant about distantly neighbouring countries, including Daxia 大夏, meaning “Greater Bactria” or “the Bactrian Empire”, i.e. Central Asia, then firmly held by the Iranian-speaking Scythians. These were a predominant influence from Croatia to Mongolia, where they imparted their lucrative knowledge of metallurgy and horse-training (Scythian legends pertaining to these skills were interiorized even by the Japanese). Their ancestral heartland was Bactria, i.e. present-day northern Afghanistan and southeastern Uzbekistan around the Amu Darya river (Greek: Oxus), an oasis friendly to agriculture and habitation amidst a harsh and inhospitable region.
The later Chinese tended to identify themselves with their ruling class. The Qin 秦dynasty (-3rd) yielded the international name China, Sanskrit Cīnā; the Han 漢 dynasty (-3rd to +3rd) lent its name to the usual self-designation of the ethnic Chinese as distinct from the minorities within China as “the Han”. It might be that a Chinese elite for some reason had identified itself with the expanding Scythians.”[...]