An Etymological Dictionary of the German Language/Annotated/rennen

by Friedrich Kluge

rennen, verb, ‘to run,’ from Middle High German and Old High German rennen, properly ‘to cause to flow, chase, drive,’ especially ‘to make a horse leap, burst,’ hence the reflexive meaning of the Modern High German word; corresponding to Old Saxon rennian, Gothic rannjan, which are factitives of rinnen.