Kumo Xi
The Kumo Xi (), also known as the Tatabi, were a Mongolic steppe people located in current Northeast China from 207 AD to 907 AD. After the death of their ancestor Tadun in 207, they were no longer called Wuhuan but joined the Khitan Xianbei in submitting to the Yuwen Xianbei. Their history is widely linked to the more famous Khitan. During their history, the Kumo Xi engaged in conflict with numerous Chinese dynasties and with the Khitan tribes, eventually suffering a series of disastrous defeats to Chinese armies and coming under the domination of the Khitans. In 907 , the Kumo Xi were completely assimilated into the Khitan-led Liao dynasty of China. Etymology. Omeljan Pritsak reconstructs the ethnonym underlying Middle Chinese *"kʰuo-mɑk̚-ɦei" as "qu(o)mâġ-ġay". The first element "qu(o)mâġ" is from *"quo" "yellowish" plus denominal suffix *"-mAk", cognate with Mongolian "qumaġ" "fine sands" and with Turkic "qumaq" and "qum". As for *"ɦei", Christopher Atwood (2010) proposed that it reflects an "i"-suffixed form of OC 胡 *gâ > "hú". Further, "gâ" is etymologically uncertain: Peter Benjamin Golden (2003) proposes several Mongolic etymologies: "ɣai" "trouble, misfortune, misery", "χai" "interjection of grief", "χai" "to seek", "χai" "to hew", albeit none  compelling. Pritsak proposes that the "qu(o)mâġ-ġay" comprised two Proto-Mongolic groups: the "Qu(o)mâġ", whom he linked to the Kimek and the Qun/Cumans (whose ethnonym possibly meant "yellow") and the "Qay" proper. However, Golden thinks that "qu(o)mâġ-ġay" simply means "desert Qay" or "sand Qay", referring to their earlier habitat. As for the exonym "Tatabï" given to Kumo Xi by Göktürks, Yury Zuev (2002) compares "Tatabï" to Avestan "tata apo" and proposes an etymology from Iranic *"tata-api" "falling waters", after having noted that the name of a Xī-(奚)-associated tribe "Bái-Xí" 白霫 (< MC *"bˠæk̚-ziɪp̚") literally meant "white  downpour/torrent" in Chinese, and that the Xī (奚) and Xí (霫) occupied the same area, Zhongjing (中京). Origin. The Kumo Xi were descendants of the Wuhuan. The "Book of the Later Han" records that “the language and culture of the Xianbei are the same as the Wuhuan”. Along with the Xianbei, the Wuhuan formed part of the proto-Mongolic Donghu confederation in the 4th century BC. The Weishu (Description of the Khitan, Vol. 1000, 2221) records that the Kumo Xi and Khitans (descendants of the Xianbei) spoke the same language. The "Book of Wei" (Description of the Khitan, Vol . 100, 2223) records : The "Book of Sui" records: The "New Book of Tang" records: History. In 388 AD, the Kumo Xi and Khitans fought with the Xianbei Northern Wei dynasty. The conflict severely weakened the Kumo Xi while the Khitans were not as badly affected, resulting in their split into separate polities. By the early Tang period (around the 7th century AD), the (now named) Xi had become subordinate to the Khitans. After the Khitans' Li-Sun Rebellion (696-697) and revolt of Ketuyu (730-734), the Xi regained their position of dominance. The Xi then entered a golden age , lasting from approximately 755 to 847. During this period the Xi were friendly with An Lushan, and supported An in his An Shi Rebellion (756-763), plundering Han territories frequently within this period. This aggressive policy seems to have consumed Xi forces, especially weakening their demographic vitality, allowing the less aggressive Khitans to dominate them. Xi raids into China provoked successive heavy responses from the Tang, resulting in battles in the 760s and in 795 that were disastrous for the Xi. After 795, the Xi became a tributary people to the Tang. The Uyghur Empire (744-840) collapsed in the  840's. When the Tang dynasty simultaneously displayed signs of division, the Xi rose in rebellion in 847, and were subsequently and disastrously defeated by Zhang Zhongwu, the frontier commander of Lulong. The Xi were never able to recover from their defeat in 847. In the late ninth century AD the Khitans rose to eventually absorb the remnants of Xi people, and established the Liao Dynasty in 907. Cultural heritage. It is believed that the "Xiqin", a bowed, stringed instrument that is the ancestor of the Chinese "Erhu", the Mongolian "Khuuchir" and "Morin khuur", was derived from a Xi instrument