The dictionary offers the vocabulary of German secret languages that have been documented over the last 20 years as part of the revival of special language research. It focuses on so-called Rotwelsch dialects, which function as secret languages through the integration of words from donor languages such as Yiddish, Romani, Romance, and Slavic languages, as well as medieval Rotwelsch. The dictionary is based on speaker interviews and written sources and is organized by word families. Each entry provides, in addition to the head lemma, written variants, definitions, usage examples, and information about the origins of the words.