She was chiefly worshiped in Nippur and nearby Tummal alongside Enlil, and multiple temples and shrines dedicated to her are attested in textual sources from these cities.
Syncretism with Sud also resulted in Ninlil acquiring some of her unique characteristics, such as an association with healing goddesses and with Sudaĝ, a name of the wife of the sun god Shamash.
In Syrian cities such as Mari, Emar and Ugarit, Ninlil was closely associated with the local goddess Shalash, the spouse of Dagan, a god regarded as analogous to Enlil.
In the Neo-Assyrian Empire Ninlil was reinterpreted as the spouse of the supreme Assyrian god Ashur, and in this role developed into Mullissu, who in turn could be identified with various deities from the pantheon of Assyria, such as Šerua or local forms of Ishtar from cities such as Nineveh.
Through most of the third millennium BCE, Ninlil's name was written with the Sumerian cuneiform sign LÍL (KID[1]), while Enlil's with identically pronounced É.
[6] A variant Akkadian form of the name was Mullilu, in Neo-Assyrian sources spelled as Mullissu, in Aramaic texts as mlš, and in Mandaic as mwlyt.
[9] A different interpretation has been suggested by Manfred Krebernik [de], who argues this entry has no relation to Sud and represents a deified cult emblem, specifically a lance (Akkadian: šukurrum).
[19] Enlil could be described as a divine merchant (ddam-gar3), which according to Jeremiah Peterson might mean that dta-am-kart-tum attested in a fragment of a non-standard Old Babylonian god list from Nippur is a name of Ninlil referring to a similar role.
[27] Ninlil was also incorporated into Hurrian religion, where she and Enlil were regarded as two of the so-called "primeval gods",[28] a group of deities belonging to the former divine generations who resided in the underworld.
[33] A different theory, based on Aramaic inscriptions from the Parthian period, makes Šerua's initial position that of a daughter of Ashur, who later came to be viewed as his second wife alongside Mullissu.
[47] While a number of sources attest that Ninlil could be regarded as the mother of Ninazu, according to Frans Wiggermann this tradition might only be a result of the growing influence of Nergal on this god's character, which was also responsible for his role as a divine warrior.
[48] He points out that in other sources Ninazu was the son of Ereshkigal and a nameless male deity, presumably to be identified with Gugalanna, which reflected his own character as a god of the underworld.
[57] Ninĝidru (written dNIN.PA; a second possible reading is Ninĝešduru[58]) fulfills the role of a sukkal in a hymn to Sud, where she is described as responsible for receiving visitors in her mistress' temple.
[63] He suggests that as the god of Kuara, Asalluhi might have been associated with Sud and Shuruppak due to both of those cities being viewed as predating the mythical great flood in Mesopotamian tradition.
[80] Multiple small shrines in Nippur were also dedicated to her, including the Ešutumkiagga ("house, beloved storeroom") built by Ur-Nammu,[81] the Emi-Tummal (translation of the first element uncertain),[82] a shrine called Abzu-Ninlil ("Apsu of Ninlil"), attested in documents from the Ur III period,[83] which according to Manfred Krebernik was a water basin,[41] and a further sanctuary distinct from those three whose name is not fully preserved, also known from documents from the Ur III period.
[87] In the Ur III period, a festival taking place in Tummal was centered on Ninlil symbolically renewing the king's legitimacy by decreeing his fate.
[91] Ninlil was also worshiped in Dur-Kurigalzu, and a temple dedicated to her, the Egašanantagal ("house of the lady on high") was built there by king Kurigalzu I from the Kassite dynasty of Babylon.
[54] The details of this process are presently unknown, though it is possible the goddess of Ḫursaĝkalamma was at this point understood not as a manifestation of Ishtar but as an ištaru, a generic term referring to female deities, and therefore could be assigned the name Ninlil without any type of syncretism occurring.
[61] Much information about the religious life of this city has been obtained from administrative texts, and it is known that in addition to Sud, deities such as Nisaba, Ninkasi, Ninmug and Ninshubur were also worshiped there.
[100] He also notes that it cannot be precisely established how long Shuruppak remained inhabited due to lack of archeological data, as erosion only left the oldest layers of the city to excavate.
[101] At the same time, he acknowledges the fact that Shuruppak retained a degree of religious importance does not necessarily indicate that it was still an administrative center or a major urban settlement in the Isin-Larsa period.
[100] It is also possible that Esiguz ("house of goat hair") located in Guaba was a temple of Sud, but this is uncertain, and it is better attested in association with Inanna of Zabalam.
[106] A further temple which seemingly was primarily dedicated to Sudaĝ but possibly could have been associated with Sud as well was Ešaba ("house of the heart"), whose location is presently unknown.
[108] Utnapishtim, the protagonist of the flood myth which forms a part of the Epic of Gilgamesh, is described as a Shuruppakean,[108] while the text referred to as Nippurian Taboos 3 in modern scholarship alludes to the belief that a confrontation between the primordial deity Enmesharra and either Enlil or Ninurta took place there.
"[113] According to Wilfred G. Lambert, both terms are rare in Mesopotamian religious literature, and presumably refer to major deities of the pantheon treated as a group.
[114] Ninlil follows him during his exile, even though he refuses to see her, and eventually ends up becoming pregnant multiple times,[115] giving birth to Nanna, Nergal, Ninazu and Enbilulu.
[122] Miguel Civil noted that the text had "wide diffusion attested not only by the relatively high number of sources preserved and their geographical distribution, but also by its long survival through Middle-Babylonian times and into the Assyrian libraries.
[120] In the beginning of the composition Enlil, who is portrayed as a young bachelor traveling to find a wife,[120] encounters Sud on the streets of Eresh and proposes to her.
[132] It is assumed that this myth represents a relic of the association between Sud, identified with Ninlil, and Sudaĝ, one of the names of the wife of sun god.
[27] Manfred Krebernik considers the composition to be the result of confusion between the names Sud and Sudaĝ, and thus between Ninlil and Ishum's mother, rather than syncretism.