What happened next was that the Jewish empire began to collapse. By the tenth century, the Jews on the Black Sea migrated to Ukraine and Italy. Yiddish became the lingua franca of these Ashkenazic Jews and absorbed German words while maintaining the Slavic grammar. And as global trade moved to the hands of the Italians, Dutch and English, the Jews were pushed aside.

Source: Ashkenazic Jews’ mysterious origins unravelled by scientists thanks to ancient DNA