An Etymological Dictionary of the German Language/Annotated/Eis
Eis, neuter, ‘ice,’ from the equivalent Middle High German and Old High German îs, neuter; a word common to Teutonic; compare Dutch ijs, Anglo-Saxon îs, English ice, Old Icelandic íss, ‘ice’ (Gothic *eisa is by chance not recorded). Outside the Teutonic group no term identical with this can be found. It is still undecided whether it is cognate with Eisen (root ī̆s ‘to shine’?) or with Zend isi (‘ice’?).