In Sumerian mythology, Nammu (also Namma, spelled ideographically d

Dingir

Dingir is a cuneiform sign, most commonly the determinative for "deity" although it has related meanings as well. As a determinative, it is not pronounced, and is conventionally transliterated as a superscript "D" as in e.g. DInanna...

NAMMA = ^dENGUR) was a primeval goddess, corresponding to Tiamat

Tiamat

In Babylonian mythology, Tiamat is a chaos monster, a primordial goddess of the ocean, mating with Abzû to produce younger gods. It is suggested that there are two parts to the Tiamat mythos, the first in which Tiamat is 'creatrix', through a "Sacred marriage" between salt and fresh water,...

 in Babylonian mythology.

Nammu was the primeval sea (Engur) that gave birth to An

Anu

In Sumerian mythology, Anu was a sky-god, the god of heaven, lord of constellations, king of gods, Consort of Antu, spirits and demons, and dwelt in the highest heavenly regions. It was believed that he had the power to judge those who had committed crimes, and that he had created the stars as...

 (heaven) and Ki

Ki (goddess)

Cuneiform KI is the sign for "earth". It is also read as GI5, GUNNI "hearth", KARAŠ "encampment, army", KISLAḪ "threshing floor" or steath, and SUR7...

 (earth) and the first gods, representing the Apsu, the fresh water ocean that the Sumerians believed lay beneath the earth, the source of life-giving water and fertility in a country with almost no rainfall.

Nammu is not well attested in Sumerian mythology.