An Etymological Dictionary of the German Language/kein

by Friedrich Kluge

kein, num. adj., ‘no, none,’ from MidHG. kein, shortened from dechein, OHG. dihhein, also OHG. dohh-ein, nihhein, nohhein, all of which are compounded with ein. The meaning of OHG. and MidHG. dech is obscure.