An Etymological Dictionary of the German Language/Annotated/Neffe
Neffe, masculine (with abnormal ff), ‘nephew,’ from Middle High German nëve, Old High German něvo, masculine; originally existing in all the Old Teutonic dialects (now obsolete in Suabian and Bavarian). The meaning in the older languages was not so definite as at present; Middle High German nëve, most frequently means ‘sister's son,’ also more rarely ‘brother's son,’ likewise ‘uncle,’ then generally ‘relative’; Dutch neef, ‘grandson, nephew, cousin,’ Anglo-Saxon nëfa, ‘grandson, nephew’ (English nephew is based on French neveu), Old Icelandic nefe, masculine, ‘relative.’ Gothic *nifa, masculine, is by chance not recorded. The cognates are primitive and common to the Aryan group; Teutonic *nefôd, nominative singular (of which there is a feminine form niftî; see Nichte), from pre-Teutonic népôt, appears in Indian nápât (stem náptṛ), ‘descendant, son, grandson,’ Latin nepos, ‘grandson,’ Greek ἀνεψιός, ‘first cousin,’ νέποδες, ‘brood,’ Old Irish nia, ‘sister’s son.’ With regard to the fluctuation of meaning see Braut, Oheim, Vetter, and Schwager.