Merkit
An Asian tribe inhabiting southeastern Siberia during the Middle Ages, regarded by their neighbours as being particularly ferocious. Their ethnicity is somewhat obscure; the balance of the evidence suggests that they were Mongolic-speaking (related to Mongols, Naimans, Keraits, and Khitan), but it has also been postulated that they are more closely related to Paleo-Asians such as the Chukchi, or Tungusic (Manchu and Evenk).
Temujin (Genghis Khan) had Merkit ties: his mother, Hoelun, was the wife of Chiledu, abducted from him by Temujin's father Yesugei. The abduction, described in detail in The Secret History of the Mongols, sparking a long-running feud. Later, Temujin's wife Borte was kidnapped by Merkit raiders and given to one of their warriors. Temujin, supported by his blood brother Jamuka and his foster-father Toghril Khan of the Keraits, attacked the Merkit and rescued Borte. Shortly thereafter she gave birth to a son; Temujin accepted paternity of the boy but named him Jochi ("the Guest") and there was always tension between the two.
During Temujin's conquest of Mongolia the Merkit were subdued; they subsequently disappear as a separate ethnic group. Those who survived the initial conquest were probably dispersed among other Mongol tribes.