least partially, Turkic and descendants of the Xiongnu. Since Guignes' time, considerable scholarly effort has been devoted to investigating such a connection. The issue remains controversial. Their relationship to other peoples known collectively as the Iranian Huns is generally accepted, but whether these groups are all inter-related remains controversial. Some scholars claimed Huns as Proto-Mongolian or Yeniseian in origin. Linguistic studies by Otto Maenchen-Helfen and others have suggested that the language used by the Huns in Europe was too little documented to be classified. Nevertheless, the majority of the proper names used by Huns appear to be Turkic in origin, though they are "far from unambiguous, so no firm conclusion can be drawn from this type of data". Steppe expansions Göktürks – Turkic Khaganate (5th–8th c.) The earliest certain mentioning of the politonym "Turk" was in the Chinese Book of Zhou. In the 540s AD, this text mentions that the Turks came to China's border seeking silk goods and a trade relationship. A Sogdian diplomat represented China in a series of embassies between the Western Wei dynasty and the Turks in the years 545 and 546. According to the Book of Sui and the Tongdian, they were "mixed barbarians" (; záhú) who migrated from Pingliang (now in modern Gansu province, China) to the Rourans seeking inclusion in their confederacy and protection from the prevailing dynasty. Alternatively, according to the Book of Zhou, History of the Northern Dynasties, and New Book of Tang, the Ashina clan was a component of the Xiongnu confederation. Göktürks were also posited as having originated from an obscure Suo state (索國), north of the Xiongnu. The Ashina tribe were famed metalsmiths and were granted land south of the Altai Mountains (金山 Jinshan), which looked like a helmet, from which they were said to have gotten their name 突厥 (Tūjué), the first recorded use of "Turk" as a political name. In the 6th-century, Ashina's power had increased such that they conquered the Tiele on their Rouran overlords' behalf and even overthrew Rourans and established the First Turkic Khaganate. The original Old Turkic name Kök Türk derives from kök ~ kö:k, "sky, sky-coloured, blue, blue-grey". Unlike its Xiongnu predecessor, the Göktürk Khaganate had its temporary Khagans from the Ashina clan, who were subordinate to a sovereign authority controlled by a council of tribal chiefs. The Khaganate retained elements of its original animistic- shamanistic religion, that later evolved into