An Etymological Dictionary of the German Language/pfropfen
pfropfen, vb., ‘to plug up, cork,’ from MidHG. pfropfen, allied to OHG. pfroffo, *pfropfo, ‘layer of a vine, slip,’ MidHG. pfropfœre, ‘graft.’ OHG. pfroffo, pfropfo, m., is derived from Lat. prō̆pâgo, m. (for the retention of the nom. form instead of the oblique case see Pfau), ‘layer, slip,’ whence also Ital. propaggine, Fr. provin. With regard to the period when the word was borrowed see Pfirsich.