The article presents the Lithuanian fishing glossary in the text of 1792 Curonian lagoon fishing rules. It discusses the problems of creation of this source, authorship, the historical context. It is analysed ethnographic content in glossary of Lithuanian fishing terms. The Baltic linguists haven’t noticed it earlier. New publication of this source could encourage scientists to broader analyze of 1792 fishing rules. It is intended to draw attention to Lithuanistic material in Prussian law documents in German language.