Historical sociolinguistics is a comparatively new area of research, investigating difficult questions about language varieties and choices in speech and writing. Jewish historical sociolinguistics is rich in unanswered questions: when does a language become 'Jewish'? What was the origin of Yiddish? How much Hebrew did the average Jew know over the centuries? How was Hebrew re-established as a vernacular and a dominant language? This book explores these and other questions, and shows the extent of scholarly disagreement over the answers. It shows the value of adding a sociolinguistic perspective to issues commonly ignored in standard histories. A vivid commentary on Jewish survival and Jewish speech communities that will be enjoyed by the general reader, and is essential reading for students and researchers interested in the study of Middle Eastern languages, Jewish studies, and sociolinguistics.