An Etymological Dictionary of the German Language/Annotated/wo

by Friedrich Kluge

wo, adverb, ‘where,’ from Middle High German and Old High German wâ for older wâr, ‘where’; compare Old Saxon hwâr, Dutch waar, Anglo-Saxon hwœ̂r, English where, and the equivalent Gothic hwar. A local adverb from the old interrogative pronoun hwa-, from Aryan ko-; compare Sanscrit kárki, ‘when.’ See wer and warum.