An Etymological Dictionary of the German Language/Annotated/Riester
Riester, masculine,. ‘wrist, instep, patch (on a shoe),’ Modern High German only; probably a primitively word, but of obscure origin. This word, which is unknown to Bavarian, has, according to Swiss riešter, rieštere, masculine and feminine, a genuine diphthong equivalent to Gothic iu; hence Middle High German altriuȥe, riuȥe, ‘cobbler,’ preserved in Modern High German dialects as Altreise, ‘second-hand dealer,’ is perhaps allied.