Sometime in the early medieval period, the Jews of central and eastern Europe came to be called by this term. In conformity with the custom of designating areas of Jewish settlement with biblical names, Spain was denominated Sefarad (Obadiah 20), France was called Tsarefat (1 Kings 17:9), and Bohemia was called the Land of Canaan. By the high medieval period, Talmudic commentators like Rashi began to use Ashkenaz/Eretz Ashkenaz to designate Germany, earlier known as Loter, where, especially in the Rhineland communities of Speyer, Worms and Mainz, the most important Jewish communities arose. Rashi uses leshon Ashkenaz (Ashkenazi language) to describe German speech, and Byzantium and Syrian Jewish letters referred to the Crusaders as Ashkenazim. Given the close links between the Jewish communities of France and Germany following the Carolingian unification, the term Ashkenazi came to refer to both the Jews of medieval Germany and France.
How did Byzantium and Syrian Jewish letters refer to the Crusaders?
as Ashkenazim