An Etymological Dictionary of the German Language/Annotated/wimmeln
wimmeln, verb, ‘to swarm, teem with,’ from late Middle High German (Middle German) wimmen, ‘to be astir, swarm.’ From the same root wem (wam) are derived the equivalent Old High German wimidôn and wimizzen (wamezzen). Old High German wiuman, ‘to swarm with,’ seems to be a reduplicated present of the same root wen (we-wm-).