An Etymological Dictionary of the German Language/falsch
falsch, adj., ‘false, wrong,’ from the equiv. MidHG. valsch, adj.; OHG. *falsc is not recorded. On account of late AS. fals, E. false, Scand. fals, which are clearly derived from Lat., the word is doubtlessly connected in some way with Lat. falsus. But since the latter retained its s unchanged (comp. Ital. falso, Fr. faux, from OFr. false), we cannot imagine that the word was borrowed directly from Lat.-Romance (OIc. falskr is a German loanword of the 15th cent.). Probably MidHG. valsch, a comparatively recent formation (comp. fein, wach), from OHG. gifalscón, gifęlscen, vb., ‘to falsify,’ which is derived from a Lat. *falsicâre; Romance *falscare, ‘to falsify.’ The assumption that MidHG. valsch (akin to vâlant, ‘demon’?) is primit. allied to Lat. fallere, Gr. σφάλλεσθαι, is scarcely valid.