On one hand, Stump(en) is the regular Central and Low German equivalent of Stumpf. Compare Middle Low Germanstump and Middle High German (Central German) stumpe. On the other hand, the same form arose as an Upper German variant of Stummel, from Old High Germanstumbal, through dialectal devoicing of -b-. The two lineages have without doubt come together in the modern word; its spread to standard German is based chiefly on Upper German usage, however.