An Etymological Dictionary of the German Language/Annotated/falsch
falsch, adjective, ‘false, wrong,’ from the equivalent Middle High German valsch, adjective; Old High German *falsc is not recorded. On account of late Anglo-Saxon fals, English false, Scandinavian fals, which are clearly derived from Latin, the word is doubtlessly connected in some way with Latin falsus. But since the latter retained its s unchanged (compare Italian falso, French faux, from Old French false), we cannot imagine that the word was borrowed directly from Latin-Romance (Old Icelandic falskr is a German loanword of the 15th century). Probably Middle High German valsch, a comparatively recent formation (compare fein, wach), from Old High German gifalscón, gifęlscen, verb, ‘to falsify,’ which is derived from a Latin *falsicâre; Romance *falscare, ‘to falsify.’ The assumption that Middle High German valsch (akin to vâlant, ‘demon’?) is primitively allied to Latin fallere, Greek σφάλλεσθαι, is scarcely valid.