They arrived in the steppes from the northern shore of the Black Sea during the 12th century, under the pressure of the Mongols. They were pushed out of Inner Mongolia into Khorasan, the Desht'i Kipchak (the Kumans' plains) and into Pannonia. Finally, they disapeared, assimilated by the indigenous peoples.
The region of Kypchakia spanning a large area between central Asia and the Caucasus is named after the Kypchaks. The word "kypchak" is named in traditional Oghuz Khan Epics.
More specifically, however, "Tatar" denominates the descendants of Kypchak and other Turkic tribes that migrated west out of Southern Siberia between the 10th and the 13th centuries.
In the 13th and 14th centuries, by some complex ethnic process, the dominating group, the Kypchaks, assimilated the other Turkic-Mongolian tribes.
Some mixed with the indigenous groups in the area where they settled, while those who retained their Kypchak identity and converted to Islam, adopted the name "Tatar".
Later, they [the Tatars] mixed with them [Kypchaks], and the land had priority over their racial and natural qualities and they [the Tatars] became like Kypchaks, as they were of the same origin with them, because the Tatars settled on their lands, married them, and remained to live on their lands.
[14] Proponents of the Kypchak thesis argue that the Kazan Tatars are direct descendants of the Tatars of the Golden Horde.
Kypchak emerged as the official language, and it was in this capacity that it had an impact on the evolution of the Bulgar language.