Until about 150 years ago, West Yiddish was the language used by Jews in Germany for their everyday affairs. It stood in close and intensive contact with the dialects of the Christian population. These dialects absorbed numerous loan-words from Yiddish, partly via the mediation of special languages like Rotwelsch ('thieves' Latin'). The dictionary is based on the responses of 108 informants and on written sources from the Bavarian region of Central Franconia. The references are studied for their etymology, semantics, morphology and phonology. Lexicological and word-geographical indications from all over the German-speaking territory are drawn upon to study their dissemination both in Yiddish and in various special languages.