An Etymological Dictionary of the German Language/Annotated/fahl
fahl, adjective, ‘dun, fawn-coloured, pale,’ from Middle High German val (genitive wes), adjective, ‘pallid, discoloured, faded, yellow, fair,’ Old High German falo (nominative falawêr); compare Old Saxon falu, Anglo-Saxon fealo (genitive fealwes), English fallow, Old Icelandic fǫlr, ‘pallid, pale’; compare falb. Allied primitively to Latin palleo, ‘to be pallid,’ pallidus, ‘pallid,’ Greek πολιός (suffix ιο as in δεξιός, Gothic taihs-wa) ‘grey,’ Old Slovenian plavŭ, ‘whitish,’ Lithuanian pàlvas, ‘tawny,’ Sanscrit palita-s, ‘grey.’ By this interpretation of the cognates the ch of Upper German falch, ‘cow or horse of fawn colour,’ gefalchet, ‘fallow,’ remains unexplained; these suggest a connection with Falke. The cognates, Italian falbo, French fauve (compare also braun, blond, blau), are derived from Teutonic.