Answer
Wexler controversially claims that Yiddish is derived from Judaeo-Slavic, a hypothetical language spoken by Jews in Central and Eastern Europe before the 10th century. This claim challenges the traditional view that Yiddish evolved from Middle High German, the language spoken by Jews in the Rhineland during the 11th and 12th centuries. Wexler's theory is based on linguistic evidence, such as the presence of Slavic vocabulary and grammatical features in Yiddish.