An/Anu, Ancient High God of the Sumerian/Akkadian Pantheon

In Sumerian, the word for ‘god,’ dingir, also means, ‘shining,’ ‘bright,’ and the sign used for writing dingir also stands for An, the Sky-god; the word also means ‘high,’ ‘Heaven.’ An is the only Sumerian deity whose ideogram is never preceded by the determinative for ‘god.’ They write dingir Enlil, ‘god Enlil,’ dingir Sin, ‘god Sin,’ etc., but never dingir An. Surely this means that An (Anu) is not only older than other deities, but An was in the beginning ‘god,’ ‘the Sky-god.’ The ideogram for writing ‘god,’ ‘high,’ ‘Heaven,’ ‘bright,’ and for the god An, was the picture of a star. In the minds of the earliest Sumerians dingir Enlil, dingir Enki, etc., really mean An-Enlil, An-Enki, etc.; that is Enlil, Enki, etc., are only easpects of the father Anu. On seals of the pictographic tablets and on painted pots of that prehistoric period, the picture of a star constantly occurs. This star sign is almost the only religious symbol in this primitive age. These facts cannot be explained without assuming monotheism in the beginning.

Langdon, Stephen H., Semitic Mythology,  p. 93.