An Etymological Dictionary of the German Language/Ahn
Ahn, m., ‘grandfather, ancestor,’ from MidHG. ane (collateral modified form ene), OHG. ano, m., ‘grandfather’; akin to the Alem. dimin. Ähni, ‘grandfather.’ Further ModHG. Ahne, MidHG. ane, OHG. ana, f., ‘grandmother.’ To these are allied ModHG. Urahn, MidHG. urane, urene, OHG. *urano, m., great-grandfather'; in OHG. alt-ano, altar-ano (for the force of ur- in Urahne see ur-). The class is peculiar to G., being foreign to the remaining Teut. dialects; comp. also Enkel — really a dimin. form — which belongs to it. There is no doubt that Lat. ănus, ‘old woman,’ is a primit. cognate. Perhaps the Teut. masculine name OHG. Anelo (AS. Onela, OIc. Ále) is allied to it.