Nonsense again. The Khazars were known as such before the conversion to Judaism. Therefore the demonym CANNOT BE HEBREW. Even less plausible is the idea that it is a call for secular Jews to become religious a thousand years after the disappearance of the Khazar state. Here's some theories included in wiki.
Gyula Németh, following Zoltán Gombocz, derived Xazar from a hypothetical *Qasar reflecting a Turkic root qaz- ("to ramble, to roam") being an hypothetical velar variant of Common Turkic kez-. With the publication of the fragmentary Tes and Terkhin inscriptions of the Uyğur empire (744-840) where the form 'Qasar' is attested, though uncertainty remains whether this represents a personal or tribal name, gradually other hypotheses emerged. Louis Bazin derived it from Turkic qas- ("tyrannize, oppress, terrorize") on the basis of its phonetic similarity to the Uyğur tribal name, Qasar. András Róna-Tas connects it with Kesar, the Pahlavi transcription of the Roman title Caesar.
So, "nomads" or "raiders", in a Turkic language, is the favoured theory. Is that not more probable?