An Etymological Dictionary of the German Language/Annotated/Weichsel
Weichsel, feminine, ‘agriot cherry,’ from the equivalent Middle High German wîhsel, Old High German wîhsila, feminine. The Teutonic character of the word is undoubted; in spite of its absence in the other dialects, it is probably derived from the Old Teutonic period (hence Italian visciola?). It is connected with Old Slovenian višnja, Lithuanian vyszna, ‘agriot cherry.’ The name of the river Vistula, ‘Weichsel’ (Latin Vistula, Anglo-Saxon Wistle), has nothing to do with the word, nor with Weichselzopf, masculine, ‘elflock, plica Polonica.’ The latter is said to have come from Poland, where matted hair is often produced by some disease; compare Polish wieszczyce, ‘elflock.’