It was under the name of Nannar that the moon-god was worshipped at Ur, the most famous and probably the oldest of the cities over which the moon-god presided.

The association of Nannar with Ur is parallel to that of Shamash with Sippar,--not that the moon-god's jurisdiction or worship was confined to that place, but that the worship of the deity of that place eclipsed others, and the fame and importance at Ur led to the overshadowing of the moon-worship there, over the obeisance to him paid elsewhere.
What further motives led to the choice of the moon-god as the patron of Ur, lies beyond the scope of our knowledge.

Due allowance must be made for that natural selection, which takes place in the realm of thought as much as in the domain of nature.

Attention has already been called to the predominance given by the Babylonians to the moon over the sun.

The latter is expressly called the "offspring of the lord of brilliant beginning," that is, the moon-god (Delitzsch, _Assyr.