The Khazarian theory is absolutely without any evidence. As any historian will tell you, generations of Jews, like generations of any people, leave some historical traces behind them. People leave behind them historical documents and archaeological data. However, archaeological evidence about the widespread existence of Jews in Khazaria is almost nonexistent. (in Israel those evidence are countless,even after more than thousand years) .
While a series of independent sources does testify to the existence in the 10th century of Jews in the Kingdom of Khazaria, and while some of these sources also indicate that the ruling elite of Khazaria embraced Judaism, the Khazarian state was destroyed by Russians during the 960s. In other words, we can be confident that Judaism was not particularly widespread in that kingdom.
The next historical record of Jews — in a few cities that today belong to western Ukraine and western Belarus — shows up in the 14th century, when Jews are regularly referred to in numerous documents.
And yet, no direct historiographical data is available to connect the Jews who lived in Eastern Europe in the 14th century with their co-religionists from the 10th-century Khazaria.
One city in northwest Ukraine, Volodymyr-Volynskyi, does seem to have an uninterrupted presence of Jews from the 12th century (not 10th). For example, in 1171 a Jewish merchant called Benjamin from that city lived in Cologne, and a Russian document refers to local Jews in 1288. Another Jewish source describes a circumcision ceremony in that city at the end of the 14th century. But it is only during the 16th century that references to Jews appear in large territories of Ukraine, Belarus and Lithuania, and even in the mid-16th century local communities were not populous. Historical documents also indicate that the earliest known Jewish communities in Poland were all situated in its westernmost part.
But history is not the only thing that debunks the Khazarian hypothesis. Linguistics, too, and the study of Yiddish help us rule out a Khazarian ancestry for today’s Jews. Since the 17th century, Yiddish was the vernacular language of all Jews of Eastern Europe. All its main structural elements are German, though during the past few centuries, they also underwent a strong influence of Slavic languages.
This view is shared by all major Yiddish linguists — but not by Paul Wexler. Wexler believes there to be certain structural Turkic and Iranian elements “hidden” in Yiddish. His methods rely heavily on fortuitous coincidences. And if you apply them more widely, you can link Yiddish to any language in the world.
It is simply bad linguistics. All words of Turkic origin came into Yiddish via the intermediary of East Slavic languages. It is the lexicon that keeps the actual traces of languages spoken by ancestors of Yiddish speakers. For that reason, in addition to Hebrew and Aramaic words, Yiddish has a small set of words whose roots come from Old French, Old Czech and Greek.
Some proponents of the Khazarian theory admit the German basis of Yiddish, but pretend that it was learned in Eastern Europe by “indigenous” Jewish masses from rabbis who came from the West and who introduced Yiddish as a “prestige” language.
But such a scenario can hardly be accepted. Only the cultural languages, Hebrew and Aramaic, were prestigious. During the 16th and 17th centuries, Yiddish brought from Central Europe became the first language for all Jews of Eastern Europe, a vernacular rather than a prestige object. Slavic idioms were used in that area by both the Christian majority and (during the previous period) by local Jews of heterogenous origins. Far from prestigious, Yiddish, understandable even for children, was used to teach students the prestigious language of Hebrew. We know that Yiddish wasn’t a prestige language, because girls, who were not taught languages in school, spoke it, too. The role of mothers in the transmission of the everyday language is by far more important than that of fathers.
In addition to history and linguistics, a third discipline can help us put to rest the Khazarian hypothesis: onomastics, or the study of proper names. Looking at names, both first names and surnames, gives us a sense of how a community saw itself, its language and its origins. And in the Jewish communities of Eastern Europe over the past six centuries, not a single Turkic name can be found in documents listing Jewish names. Even in documents from the 15th and 16th centuries dealing with Jews who lived in the territories of modern Ukraine and Belarus have no such names.
In the corpus of given names used by Jews of Eastern Europe during the last centuries, we find the same linguistic layers as in the lexicon of Yiddish. There are numerous Germanic and Hebrew names and some Aramaic names. There are also Greek names (Todres from Theodoros, Kalmen from Kalonymos), Old French names (Beyle, Bunem, Yentl), Old Czech names (Khlavne, Slave, Zlate), and Polish names (Basye, Tsile), and very few East Slavic names (Badane, Vikhne). There are no Turkic names.
Via Alexander Beider Forward.com