An Etymological Dictionary of the German Language/Annotated/Reisigen

by Friedrich Kluge

Reisigen, plural, ‘horsemen,’ usually connected with Middle High German reise, ‘military expedition,’ yet it may be also a derivative of rîten, ‘to ride,’ since Old High German rîso, ‘horseman,’ occurs (rîþtan- gives rîssan-, rîsan-).