Thorkild Jacobsen and Walter Burkert both argue for a connection with the Akkadian word for sea, tâmtu, following an early form, ti'amtum. Burkert continues by making a linguistic connection to Tethys. The later form Θαλάττη (thaláttē), which appears in the Hellenistic Babylonian writer Berossus' first volume of universal history, is clearly related to Greek Θάλαττα (thálatta), an Eastern variant of Θάλασσα (thalassa), "sea". It is thought that the proper name ti'amat, which is the construct or vocative form, was dropped in secondary translations of the original texts because some Akkadian copyists of Enûma Elish substituted the ordinary word tāmtu "sea" for Tiamat, the two names having become essentially the same due to association. Tiamat also has been claimed to be cognate with Northwest Semitic tehom (תהום) (the deeps, abyss), in the Book of Genesis 1:2.
The Babylonian epic Enuma Elish is named for its incipit: "When above" the heavens did not yet exist nor the earth below, Apsu the freshwater ocean was there, "the first, the begetter", and Tiamat, the saltwater sea, "she who bore them all"; they were "mixing their waters". It is thought that female deities are older than male ones in Mesopotamia and Tiamat may have begun as part of the cult of Nammu, a female principle of a watery creative force, with equally strong connections to the underworld, which predates the appearance of Ea-Enki.
Harriet Crawford finds this "mixing of the waters" to be a natural feature of the middle Persian Gulf, where fresh waters from the Arabian aquifer mix and mingle with the salt waters of the sea. This characteristic is especially true of the region of Bahrain, whose name in Arabic means "two seas", and which is thought to be the site of Dilmun, the original site of the Sumerian creation beliefs. The difference in density of salt and fresh water drives a perceptible separation.