If I'm not mistaken, the Sumerians called themselves as 𒊕𒈪𒂵 (saĝ-gíg-ga) and their country as 𒆠𒂗𒄀 (k-en-gi(-r), how would you turn that into an adjectival form or demonym like how -n is added to America to turn it into an adjectival form denoting to the American people, culture, etc.?
Similarly, how would demonyms be formed in Akkadian?