An Etymological Dictionary of the German Language/fahl
fahl, adj., ‘dun, fawn-coloured, pale,’ from MidHG. val (gen. wes), adj., ‘pallid, discoloured, faded, yellow, fair,’ OHG. falo (nom. falawêr); comp. OSax. falu, AS. fealo (gen. fealwes), E. fallow, OIc. fǫlr, ‘pallid, pale’; comp. falb. Allied primit. to Lat. palleo, ‘to be pallid,’ pallidus, ‘pallid,’ Gr. πολιός (suffix ιο as in δεξιός, Goth. taihs-wa) ‘grey,’ OSlov. plavŭ, ‘whitish,’ Lith. pàlvas, ‘tawny,’ Sans. palita-s, ‘grey.’ By this interpretation of the cognates the ch of UpG. falch, ‘cow or horse of fawn colour,’ gefalchet, ‘fallow,’ remains unexplained; these suggest a connection with Falke. The cognates, Ital. falbo, Fr. fauve (comp. also braun, blond, blau), are derived from Teut.