Louis Bazin derived it from Turkic qas- ("tyrannize, oppress, terrorize") on the basis of its phonetic similarity to the Uyğur tribal name, Qasar.
The objections are that Uyğur Gesa/Qasar was not a tribal name but rather the surname of the chief of the Sikari tribe of the Toquz Oğuz, and that in Middle Chinese the ethnonym "Khazars", always prefaced with the word Tūjué (Tūjué Kěsà bù:突厥可薩部; Tūjué Hésà:突厥曷薩), is transcribed with characters different from those used to render the Qa- in the Uyğur word 'Qasar'.
Whereas the royal or ruling elite probably spoke an eastern variety of Shaz Turkic, the subject tribes appear to have spoken varieties of Lir Turkic, such as Oğuric, a language variously identified with Bulğaric, Chuvash, and Hunnish (the latter based upon the assertion of the Persian historian al-Iṣṭakhrī that the Khazar language was different from any other known tongue).
Many Turkic groups, such as the Oğuric peoples, including Šarağurs, Oğurs, Onoğurs, and Bulğars who earlier formed part of the Tiĕlè (鐵勒) confederation, are attested quite early, having been driven West by the Sabirs, who in turn fled the Asian Avars, and began to flow into the Volga-Caspian-Pontic zone from as early as the 4th century CE and are recorded by Priscus to reside in the Western Eurasian steppelands as early as 463.
The native religion of the Khazars is thought to have been Tengrism, like that of the North Caucasian Huns and other Turkic peoples.
but the scope of the conversion within the Khazar Khanate remains uncertain.
By 568, these Göktürks were probing for an alliance with Byzantium to attack Persia.
An internecine war broke out between the senior eastern Göktürks and the junior West Turkic Qağanate some decades later, when on the death of Taspar Qağan, a succession dispute led to a dynastic crisis between Taspar's chosen heir, the Apa Qağan, and the ruler appointed by the tribal high council, Āshǐnà Shètú (阿史那摄图), the Ishbara Qağan.
In the late 19th century, a theory emerged that the core of today's Ashkenazi Jews descended from a hypothetical Khazarian Jewish diaspora who had migrated westward from modern Russia and Ukraine into modern France and Germany.Though anachronistic in retrodating the Khazars to this period, the legend, in placing the Khazar qağan on a throne with equal status to kings of the other two superpowers, bears witness to the reputation won by the Khazars from early times.