An Etymological Dictionary of the German Language/Annotated/Sehne
Sehne, feminine, ‘sinew, tendon, nerve, string (of a bow),’ from Middle High German sëne, sënewe, feminine, ‘sinew, string (of a bow), nerve,’ Old High German sënawa, feminine, ‘sinew’; compare Dutch zenuw, Anglo-Saxon sinu, feminine, and the equivalent English sinew, Old Icelandic sin, feminine; Gothic *sinawa, feminine, is wanting. The word is usually connected with Sanscrit snâva-s, masculine, ‘sinew’ (the Teutonic words would also imply a Sanscrit *sanâva-); its kinship with Greek ἶν-ες, ‘sinew,’ is improbable.