From Kazakhstan Encyclopedia
Toquz Oghuz (Old Turkic: 10px10px10px 10px10px10px10px Toquz Oγuz) was a political alliance of nine Turkic tribes in Inner Asia, during the early Middle Ages. Toquz Oghuz was consolidated within the Turkic Kaganate (552-743), and remained after the Kaganate fragmented.
Oghuz is a Turkic word meaning "community" and toquz means "nine". Similarly the Karluks were also known as the Uch-Oguz – uch meaning "three". The root of the generalized ethnical term "oghuz" is og-, meaning "clan, tribe", which in turn descends from the ancient Turkic word og, meaning "mother". Initially the oguz designated "tribes" or "tribal union", and eventually became an ethnonym.
The Toquz Oghuz were perhaps first mentioned in the Orkhon inscriptions, written in the 730s. The nine tribes were named in Chinese histories as the Uighurs, the Bukhu, the Khun, the Bayirku, the Tongra, Ssu-chieh (or Sitsze), Ch'i-pi, A-pu-ssu, and Ku-lun-wu-ku. The first seven named – who lived north of the Gobi Desert – were dominant, whereas the A-pu-ssu and Ku-lun-wu-ku emerged later and were accepted on an equal footing with the others some time after 743. The A-pu-ssu apparently originated as a sub-tribal group within the Ssu-chieh, and the Ku-lun-wu-ku as a combination of two other tribes.
According to Yury Zuev, Ssu-chieh or Sitsze may be a Chinese derivation of an endonym with a root in igil – a Turkic root meaning "many" (i.e. ssu-chieh < γiei-kiet < igil ). As such, Zuev has suggested, the tribe may be linked to the Uokil.