LTReikšminiai žodžiai: Senoji rusų kalba; Baltų kalbos; Toponimai; Etimologija; Hidronimai; (Old) Russian language; Baltic languages; Toponymics; Etymology; Hydronym; Basin of the Don Baltic substrate.
ENThis article deals with etymologies of five hydronyms in the basin of the Upper Don that, according to the author, are of Baltic origin: Kosorža (the old form is Kosoža)