While the Karakhanid state remained in this territory until its conquest by Genghis Khan, the Turkmen group of tribes was formed around the core of westward Oghuz. The name "Turkmen" originally simply meant "I am Turk" in the language of the diverse tribes living between the Karakhanid and Samanid states. Thus, the ethnic consciousness among some, but not all Turkic tribes as "Turkmens" in the Islamic era came long after the fall of the non-Muslim Gokturk (and Eastern and Western) Khanates. The name "Turk" in the Islamic era became an identity that grouped Islamized Turkic tribes in contradistinction to Turkic tribes that were not Muslim (that mostly have been referred to as "Tatar"), such as the Nestorian Naiman (which became a major founding stock for the Muslim Kazakh nation) and Buddhist Tuvans. Thus the ethnonym "Turk" for the diverse Islamized Turkic tribes somehow served the same function as the name "Tajik" did for the diverse Iranian peoples who converted to Islam and adopted Persian as their lingua-franca. Both names first and foremost labeled Muslimness, and to a lesser extent, common language and ethnic culture. Long after the departure of the Turkmens from Transoxiana towards the Karakum and Caucasus, consciousness associated with the name "Turk" still remained, as Chagatay and Timurid period Central Asia was called "Turkestan" and the Chagatay language called "Turki", even though the people only referred to themselves as "Mughals", "Sarts", "Taranchis" and "Tajiks". This name "Turk", was not commonly used by most groups of the Kypchak branch, such as the Kazakhs, although they are closely related to the Oghuz (Turkmens) and Karluks (Karakhanids, Sarts, Uyghurs). Neither did Bulgars (Kazan Tatars, Chuvash) and non-Muslim Turkic groups (Tuvans, Yakuts, Yugurs) come close to adopting the ethnonym "Turk" in its Islamic Era sense. Among the Karakhanid period Turkmen tribes rose the Atabeg Seljuq of the Kinik tribe, whose dynasty grew into a great Islamic empire stretching from India to Anatolia.