An Etymological Dictionary of the German Language/Fohlen
Fohlen, n., ‘foal,’ from MidHG. vol, vole, OHG. folo, m., ‘colt, foal’; comp. Goth. fula, m., ‘foal (of an ass),’ OIc. fole, ‘foal’ (of a horse, rarely of an ass), AS. fola, m., E. foal; a term common to Teut. for the young of a horse or an ass, derived from pre-Teut. pelón-, Related by gradation to Gr. πῶλος, ‘colt,’ as a general term ‘young animal,’ and Lat. pullus, ‘the young,’ especially of fowls. See Füllen.