An Etymological Dictionary of the German Language/Annotated/stumm

by Friedrich Kluge

stumm, adjective, ‘dumb, silent,’ from the equivalent Middle High German and Old High German (and Old Saxon) stum (mm); corresponding to Dutch stom, ‘dumb.’ Its connection with the cognates of stammeln (root stam) is undoubted. Middle High German stęmmen, Old High German stęmmen (from stamjan), ‘to stop, check’ (compare stemmen and ungestüm), shows that stammeln and stumm sein mean literally ‘to falter (in speaking).’