An Etymological Dictionary of the German Language/Oheim
Oheim, Ohm, m., from the equiv. MidHG. ôheim, œheim (also with final n instead of m), OHG. ôheim, m., ‘uncle’; corresponding to Du. oom, AS. eám, ‘uncle’ (contracted from *eáhâm), MidE. œ̂m, ‘uncle,’ also early ModE. eme (whence, Eames as a prop. name). By inference from OFris. êm, ‘mother's brother,’ and Lat. avunculus, the lit. meaning of Oheim is ‘uncle on the mother's side’ (in contrast to Vetter, Lat. patruus). Goth. *áuháims, corresponding to the simply West Teut. cognates, is wanting. The etymology of the word is difficult to determine. The first syllable is generally regarded as cognate with Lat. avun-culus, ‘uncle,’ which is the dimin. of avus, ‘grandfather’ (so too Lith. avynas and OSlov. ujĭ, from *aujos, ‘uncle’); to Lat. avus (to which OIr. aue, ‘grandson,’ is allied), Goth. awô, f., ‘grandmother,’ OIc. áe, ‘great-grandfather,’ corresponds. With reference to the second syllable a Teut. haima-, ‘honour,’ is assumed; therefore Oheim means lit. ‘enjoying the honours of a grandfather.’ A more probable assumption is ‘possessing the grandfather's house,’ ‘grandfather's heir’ (hence Lat. avunculus, lit. ‘little grandfather’). Others join the h to the first syllable and regard it as the representative of the Lat. c in avuncu-lus, and divide the Goth. word thus, *auh-aims, so that aima is a dimin. suffix for aina. It is to be observed that after the remarks under Neffe and Vetter, MidHG. óheim may also mean ‘nephew, sister's son.’