-ոյ

Etymology 1
From, and partly perhaps from the genitive singular case ending  (see Etymology 2).

Etymology 2
From the thematic singular genitive ending, taken over from the pronominal declension. Cognate with 🇨🇬, 🇨🇬, Homeric 🇨🇬, Old 🇨🇬, 🇨🇬 and 🇨🇬.