An Etymological Dictionary of the German Language/Klepper

by Friedrich Kluge

Klepper, m., ‘nag,’ early ModHG., orig. not in a contemptuous sense; a LG. form; it is connected with LG. kleppen, ‘to strike rapidly’ (espec. also ‘to ring with a sharp sound’), MidHG. klepfen. Perhaps the term Klepper is derived from the bells on the harness of the horse.