An Etymological Dictionary of the German Language/Annotated/Tochter
Tochter, feminine, ‘daughter,’ from the equivalent Middle High German tohter, Old High German tohter, feminine; a common Teutonic, and also a primitively Aryan term; compare Gothic daúhtar, Anglo-Saxon dohtor, English daughter, Dutch dochter, Old Saxon dohtar, ‘daughter.’ The primit Aryan dhuktêr (dhugatêr), on which the Teutonic cognates are based, is indicated also by Lithuanian duktě, Old Slovenian dŭšti; compare further Greek θυγάτηρ, Sanscrit duhitâr, Zend duγδar, ‘daughter.’ The Aryan word is usually considered to be a derivative of the Sanscrit root dugh, ‘to milk,’ regarding Tochter as equivalent to ‘milker.’ This assumption is, however, quite as dubious as the derivation of Vater, Mutter, and Bruder.