Probably ultimately from Proto-Indo-European *ǵʰh₂éns. The Latin term may have emerged from a pre-form *hāns ~ *hānsos, which perhaps had an accusative singular form *hānesem. This accusative form would then have evolved into *hānerem, which was then possibly remolded into *hānserem on the basis of the genitive singular form. It is perhaps possible that this accusative singular form then served to introduce -er- into the rest of the inflectional paradigm. Cognates include Sanskrit हंस (haṃsa), Ancient Greek χήν (khḗn), Russian гусь (gusʹ), Old Irish géiss, Old English gōs (English goose), and Albanian gatë (“heron”).