Once again, delving into origins:


Etymology

Map from Kashgari‘s Diwan (11th century), showing the distribution of Turkic tribes.

The first known mention of the term Turk (Old Turkic: 𐱅𐰇𐰼𐰰 Türük or 𐱅𐰇𐰼𐰰:𐰜𐰇𐰛 Kök Türük, Chinese: 突厥, Pinyin: Tūjué < Middle Chinese *tɦut-kyat < *dwət-kuɑt, Old Tibetan: drugu)[42][43][44][45] applied to only one Turkic group, namely, the Göktürks,[46]who were also mentioned, as türüg ~ török, in the 6th-century Khüis Tolgoi inscription, most likely not later than 587 AD.[47][48][49] A letter by Ishbara Qaghan to Emperor Wen of Sui in 585 described him as “the Great Turk Khan”.[50][51] The Bugut (584 CE) and Orkhon inscriptions (735 CE) use the terms Türküt, Türk and Türük.[52]

From https://en.m.wikipedia.org/wiki/Turkic_peoples#