Where does “stum” come from?

stum (Danish) comes from Middle Low German stum, from German stumm, from Middle High German stum, from Old High German stum, from Proto-Germanic stummaz, from Proto-Indo-European stm̥Hnós, from Proto-Indo-European stemH- — to push, inhibit, stutter, stammer.

stum (Danish): mute, not possessing the ability of speech;...