According to the traditional point of view, the ancestors of all Ashkenazi Jews (including those from Eastern Europe) lived in the Middle Ages in the Rhineland, western Germany. This consideration is supported by the religious rite practiced by Ashkenazim that originated in the area in question. The provenance from Germany seems also to be confirmed by the daily use of Yiddish, a language whose German basis is on the surface. Further analysis of this language and the given names used by Jews in Eastern Europe reveals a more nuanced picture. Alongside the real migrants from the Rhineland, we find traces of Jewish ancestors who spoke Slavic languages in the Middle Ages and lived in the Czech lands as well as in the territories of modern western Ukraine and western Belarus.