Yabghu
Yabghu (, Traditional Chinese: 葉護, Simplified Chinese: 叶护, Jabgu, Djabgu,) or Yabgu was a state office in the early Turkic states, roughly equivalent to viceroy. The title carried autonomy in different degrees, and its links with the central authority of Khagan varied from economical and political subordination to superficial political deference. The title had also been borne by Turkic princes in the upper Oxus region in post-Hephthalite times. The position of Yabgu was traditionally given to the second highest member of a ruling clan (Ashina), with the first member being the Kagan himself. Frequently, Yabgu was a younger brother  of the ruling Kagan, or a representative of the next generation, called Shad (blood prince). Mahmud Kashgari defined the title Yabgu as "position two steps below Kagan", listing heir apparent Shad a step above Yabgu. As the Khaganate decentralized, the Yabgu gained more autonomous power within the suzerainty, and historical records name a number of independent states with "Yabgu" being the title of the supreme ruler. One prominent example was the Oguz Yabgu state in Middle Asia, which was formed after the fragmentation of the Second Türkic Kaganate in the 740s. Another prominent example was the Karluk Yabghu, the head  of the Karluks which in the 766 occupied Suyab in the Jeti-su area, and eventually grew into a powerful Karakhanid state. Etymology. There are at least several proposals regarding the origin of "yabgu":