Semitic languages
The similarity of the Hebrew, Arabic and Aramaic languages was accepted by Jewish and Islamic scholars since medieval times. The languages were familiar to Western European scholars due to historical contact with neighbouring Near Eastern countries and through Biblical studies, and a comparative analysis of Hebrew, Arabic, and Aramaic was published in Latin in 1538 by Guillaume Postel. Almost two centuries later, Hiob Ludolf described the similarities between these three languages and the Ethiopian Semitic languages. However, neither scholar named this grouping as "Semitic".
Medieval Hebrew
Mention should also be made of the letters preserved in the Cairo geniza, which reflect the Arabic-influenced Hebrew of medieval Egyptian Jewry. The Arabic terms and syntax that appear in the letters constitute a significant source for the documentation of spoken medieval Arabic, since Jews in Islamic lands tended to use colloquial Arabic in writing rather than classical Arabic, which is the Arabic that appears in Arabic medieval sources.