The first reference to "Türk" or "Türküt" appears in 6th century Chinese sources as the transcription "Tūjué" (突厥). The earliest evidence of Turkic languages and the use of "Turk" as an endonym comes from the Orkhon inscriptions of the Göktürks () in the early 8th century. Many groups speaking 'Turkic' languages never adopted the name "Turk" for their own identity. Among the peoples that came under Göktürk dominance and adopted its political culture and lingua-franca, the name "Turk" wasn't always the preferred identity. Turk therefore did not apply to all Turkic peoples at the time, but only referred to the Eastern Turkic Khaganate, while the Western Turkic Khaganate and Tiele used their own tribal names. Of the Tiele, the "Book of Sui" mentions only tribes which were not part a part of the First Turkic Khaganate. There wasn't a unified expansion of Turkic tribes. Peripheral Turkic peoples in the Göktürk Empire like the Bulgars and even central ones like the Oghuz and Karluks migrated autonomously with migrating traders, soldiers and townspeople.