Yabaku is a fairly enigmatic tribe out of ten prominent Türkic tribes enumerated byMahmut Kashgari (11th century) in the list describing the location of the Türkic polities from the borders of theEastern Roman Empire to the borders of China in the following sequence:
Yabāqu can be related etymologically to Turkicyapağu, "originally denoting 'matted hair or wool' and then an animal characterized by this, e.g. a 'colt.' Zoonyms or hipponyms are known in Turkic ethnonymy, some of probable totemic origin."[1] Kashgari noted that "Among the nomadic peoples are theČömül - they have a gibberish (raṭāna [رَطَانَة]) of their own, but also know Turkic; alsoQāy,Yabāqu,Tatār andBasmil - each of these groups has its own language, but they also know Turkic well".[2] According toGolden,TurkicYabâqu/Yapağu was probably translated from, or a Turkic rendition of, an ethnonym of a bilingual people "with a complex ethno-linguistic heritage".[3]
Additionally, Kashgari namedYapâqu suw as a river flowing overKashgar from mountains inFerghana; and theHudud al-Alam also mentioned a *Yabağu river[a] near Özkend. These facts pointed to Yabakus' presence in Ferghana since at least the 10th century, if not earlier. Kashagari mentioned another river in the Yabaqu steppes - namely, the Yamar river, whichVasily Bartold identified with theEmil.[4]
According to Kashgari, Yabaku chief Böke Budrach led a pagan coalition from Western Siberia or further east across theIrtysh river to wars againstIslamicKara-khanid khanate (comprising modern Western and EasternTurkestan); Karakhanid heroic epics also mentioned these invasions, which Karakhanids thwarted successfully. According to Al-Utbi andAli ibn al-Athir, the coalition's invasions began around the 1010s (or later in the 1030s) from the direction ofṢîn, i.e. Northern China.[5][b] However, Budrach's coalition, which outnumbered the Karakhanid army, was still defeated by Toghan Khan (r. 998 - 1017/1018), who died shortly after his victory. Kashgari cited a witness, who related that Ghazi Arslan Tegin defeated the Yabaku-led coalition and captured Budrach.[6][7]
Golden proposes that the authority of the Yabaqu, as the coalition's leading tribe, extended also to their allies the Basmils and the Qays. Noting that Kashgari glossed Budrach's epithetBöke as "large dragon (ṯu'bān 'aẓim)"[8] - which might also mean "great snake", Golden further identifies Budrach's coalition, as "People of the Chieftain named Snake/Dragon", with the "Snake People" who had driven out the "Pale Ones" (xartêš), causing the "Pale Ones" to dislodge theOghuz Turks, who in turn expelled thePechenegs, in the account given byMatthew of Edessa. Golden contends that: if "Snake People" in Matthew's account were to be identified with the Qays in a parallel account byal-Marwazi), then that's because the Qays participated in the coalition led by chief Budrach, nicknamedBöke - Snake/Dragon - "a kind of honorific associated with outstanding warriors"; not becauseQay itself meant "snake" inMongolic.[c][9]