An Etymological Dictionary of the German Language/Annotated/Qual

Qual, feminine, ‘torment, pain,’ from Middle High German quâl, quâle (kále), Old High German and Old Saxon quâla, feminine, ‘anguish, torture’; compare Dutch kwaal, ‘pain,’ Anglo-Saxon cwalu, ‘violent death.’ To this word is allied a strong root verb Old High German quëlan (Middle High German quëln), ‘to be in violent pain’ (Anglo-Saxon cwëlan, ‘to die’), of which the factitive is Modern High German quälen, Middle High German quęln, Old High German quęllen (from *qualljan), ‘to torture, torment to death.’ The Teutonic root qel (qal) is primitively connected with Lithuanian gelti, ‘to prick’ (gélia, ‘it pains’), gėlà, ‘pain,’ Old Slovenian žalĭ, ‘hurt’ (Aryan root gē̆l).