An Etymological Dictionary of the German Language/Annotated/Schale
Schale, feminine, ‘shell, peel, scale, dish,’ from Middle High German schū̆l, schū̆le, Old High German scū̆la, feminine, ‘husk of fruit, egg-shell, &c., drinking cup’ (hence French écale, ‘egg-shell, nut-shell’). It is questionable whether the two different senses are evolved from the same word. It is at all events probable that one of the meanings was connected with a form containing ă (in the sense of ‘husk’), the other with a form containing â, just as North Frisian distinguishes skal (originally ă), ‘‘scale of animals,’ &c., from skeel (originally â, ê), ‘bowl.’ Compare Old Saxon scâla, feminine, ‘drinking cup,’ Anglo-Saxon sčeălu, ‘husk,’ English shale and (under Old Icelandic influence?) scale, Old Icelandic skál, feminine, ‘drinking cup, scale (of a balance).’ Akin to Gothic skalja, feminine, ‘tile’ (literally perhaps ‘shingle, similar to a scale’), Old Icelandic skel, feminine, Anglo-Saxon sčyll, feminine, English shell, Dutch schel, feminine, ‘shell, husk.’ The Gothic and Teutonic form skalja passed into Romance; compare Italian scalgia, French écaille, ‘scale, shell, crust.’ The Teutonic cognates are usually connected with an Aryan root skel, ‘to split’; compare Schelle, as well as Lithuanian skélti, ‘to split,’ Old Slovenian skolĭka, ‘mussel, shell-fish,’ Russian skala, ‘crust.’—