the origin of the Kazars is obscure. Their name seems to be connected with the eastern transmission of the name and later title Caesar.
Is it though? I don’t know at what point this particular group of Turks came to be known as “Khazars”, but I do know that although in the author’s native language (Hungarian), the name begins with a “k”, in most other languages, a fricative is implied. I can’t help but connect this to the verb חזר, which holds a similar meaning to the Turkic tön-, as in dönme.
It’s hard to tell which is less sound as a theory: That the kingdom would be referred to as “the Cæsar” (and was the only kingdom thus known in Arab records), or that the kingdom was referred to in such a way that presumes a Hebrew calque of a Turkic term for conversion. I, for one, would certainly be open to evidence for or against either of these, or any alternative theory.
Regardless of the origin of the name, the Khazars remain noteworthy even outside of the realm of Judaic history due to their having lent their name to a particularly Turk-surrounded sea: the Caspian. Unfortunately, some languages, such as Kazakh, are in the process of forgetting the most Turkic of this sea’s many names in favour of its most European. So while it is possible to find reference to the “Хазар теңізі” (Xazar teñizi) on the Kazakh internet, maps, wikipedia, and most Kazakhs I talk to agree on the predictably Russian-based and not-so-Turkic moniker of “Каспий теңізі” (Kaspïy teñizi).