“Of equal antiquity with the religion of Egypt, that of Babylonia and Assyria possesses some marked differences as to its development.
Beginning among the non-Semitic Sumero-Akkadian population, it maintained for a long time its uninterrupted development, affected mainly by influences from within, namely, the homogeneous local cults which acted and reacted upon each other.
The religious systems of other nations did not greatly affect the development of the early non-Semitic religious system of Babylonia. A time at last came, however, when the influence of the Semitic inhabitants of Babylonia and Assyria was not to be gainsaid, and from that moment, the development of their religion took another turn.
In all probably this augmentation of Semitic religious influence was due to the increased numbers of the Semitic population, and at the same period the Sumero-Akkadian language began to give way to the Semitic idiom which they spoke.
When at last the Semitic Babylonian language came to be used for official documents, we find that, although the non-Semitic divine names are in the main preserved, a certain number of them have been displaced by the Semitic equivalent names, such as Šamaš for the sun-god, with Kittu and Mêšaru (“justice and righteousness”) his attendants; Nabú (“the teacher” = Nebo) with his consort Tašmêtu (“the hearer”); Addu, Adad, or Dadu, and Rammanu, Ramimu, or Ragimu = Hadad or Rimmon (“the thunderer”); Bêl and Bêltu (Beltis = “the lord” and “the lady” /par excellence/), with some others of inferior rank.
In place of the chief divinity of each state at the head of each separate pantheon, the tendency was to make Merodach, the god of the capital city Babylon, the head of the pantheon, and he seems to have been universally accepted in Babylonia, like Aššur in Assyria, about 2000 B.C. or earlier.”
Theophilus G. Pinches, The Religion of Babylonia and Assyria, London, 1906, pp. 4-5.