Kumo Xi
According to sinologists Denis C. Twitchett and Klaus-Peter Tietze, it is generally held that the Khitans emerged from the Yuwen branch of the Xianbei people. Following a defeat at the hands of another branch of the Xianbei in 345, the Yuwen split into three tribes, one of which was called the Kumo Xi. In 388 the Kumo Xi itself split, with one group remaining under the name Kumo Xi and the other group becoming the Khitans. This view is partially backed up by the "Book of Wei", which describes the Khitans being of Xianbei origins. Beginning in the Song dynasty, some Chinese scholars suggested that the Khitans might have descended from the Xiongnu people. While modern historians have rejected the idea that the Khitan were solely Xiongnu in origin, there is some support for the claim that they are of mixed Xianbei and Xiongnu origin. Beginning with Rashid-al-Din Hamadani in the fourteenth century, several scholars have theorized that the Khitans were Mongolic in origin, and in the late 19th century, Western scholars made the claim that the Khitans were Tungusic in origin—modern linguistic analysis has discredited this claim. Many similar words exist between Khitan and Koreanic languages that are not found in Tungusic or Mongolic languages.