An Etymological Dictionary of the German Language/Annotated/pfropfen
pfropfen, verb, ‘to plug up, cork,’ from Middle High German pfropfen, allied to Old High German pfroffo, *pfropfo, ‘layer of a vine, slip,’ Middle High German pfropfœre, ‘graft.’ Old High German pfroffo, pfropfo, masculine, is derived from Latin prō̆pâgo, masculine (for the retention of the nominative form instead of the oblique case see Pfau), ‘layer, slip,’ whence also Italian propaggine, French provin. With regard to the period when the word was borrowed see Pfirsich.