Patron deity of the city of Kazallu, he was the son of the moon god Nanna/Suen.
Numušda had aspects related to nature and fertility but he was also closely connected to the gods Meslamtaea, Ninazu, and Marduk. In the third millennium BCE he appears to have been associated with underworld deites (Cavigneaux and Krebernik 1998-2001d: 612), but later this function seems to disappear.
Most of our information about Numušda's functions come from a hymn to the god written in the name of king Sin-iqišam of Larsa (r. 1840-1836 BCE). In addition to fertility and nature functions, he was apparently associated with warfare: "(Numušda), foremost in warfare, (it is) you, who can compete with you?" (Hymn to Sin-iqišam A, ETCSL 18.104.22.168, line 17).
Astronomically, Numušda was part of the constellation Centaur (Cavigneaux and Krebernik 1998-2001d: 613).
Numušda was considered to be the son of the moon god Nanna/Suen and his wife Ningal, though this filiation does not appear in his third millennium attestations. His wife was the goddess Namrat ("Shining One"), and his daughter was the goddess Adgar-kidu, who was married to the god Amurru/Martu. Their marriage is narrated in the mythological tale The Marriage of Martu (ETCSL 1.7.1).
Numušda's main cult places were the cities of Kazallu and Kiritab, neither of which have been located yet (for possible locations see Edzard 1976-1980a). On the city of Kiritab see Gragg 1973: 70. The history of Kazallu and its changing alliances and conflicts with southern Babylonia is complicated, mainly due to lack of written sources from the city itself.
The apex of Numušda's worship appears to have been the Early Dynastic period (Cavigneaux and Krebernik 1998-2001d: 613). During the Ur III period, Kazallu seems to have enjoyed good relations with the Ur III rulers, as attested in some royal inscriptions of Ur III rulers dedicated to Numušda. In the Old Babylonian period this situation changed. Year name 2b of Sin-iqišam (r. 1841-1847 BCE) mentions that the king brought statues of Numušda, Namrat, and Lugal-apiak into the city of Kazallu, but the fifth year name already reports that the king had destroyed the city.
Although Numušda was considered to be the son of the moon god Nanna/Suen, there is very little evidence for Numušda's worship in Ur, the city whose patron deity was the moon god. This led Richter (2004: 445) to assume that the familial relationship between the moon god and Numušda was not a tradition native to the city of Ur.
Numušda is first attested in the Early Dynastic IIIa period and appears in several god lists (Cavigneaux and Krebernik 1998-2001d: 612). Already by the Old Babylonian period there are but few attestations of this deity. After this he only survives into the first millennium within scholarly circles, mainly as an astral deity (Cavigneaux and Krebernik 1998-2001d: 613).
Thus far, nothing is known about Numušda's iconography.
Thus far it has been impossible to explain Numušda's name etymologically, leading to the assumption that it the name is not Sumerian (Cavigneaux and Krebernik 1998-2001d: 612). Various native folk etymologies of Numušda as a star explain the name as "Numušda: he who lets it rain constantly," "Numušda = creatures," "Numušda = the crier" (Cavigneaux and Krebernik 1998-2001d ibid.).
Nicole Brisch, 'Numušda (god)', Ancient Mesopotamian Gods and Goddesses, Oracc and the UK Higher Education Academy, 2016 [http://oracc.museum.upenn.edu/amgg/listofdeities/numuda/]