Ningirsu does not seem to be a storm god.
Here is a quote from the "deities" thread taken from the book
A Dictionary of Ancient Near Eastern Mythology
by Gwendolyn Leick,
first published 1991 by Routledge
Ningirsu—Sumerian god
His name means ‘lord of Girsu’, a city belonging to the district of Lagash.
Ningirsu was an ancient local god; he first appears in the Fara god-list
and was worshipped by all the kings of Lagash. Typically, Eannatum
and Uruinimgina call the boundaries of their territory the ‘limits of
Ningirsu’ and any destruction of their land was a sin against its god.
With Uruinimgina’s political success, the god became more widely known
in Sumer. Ningirsu as a city-god is not only a warrior, who calls the
ruler to defend his boundaries, but is also in charge of the fertility of his
‘beloved fields’. Numerous artefacts, such as mace-heads, statues, vases
etc. have been dedicated to Ningirsu; several canals and waterways
bore his name. There were of course many festivals in his honour and
he is well represented among the gods chosen for personal names. His
temple was the famous É-ninnu, the reconstruction of which during the
Neo-Sumerian period was described by Gudea. The god appeared to
Gudea in a dream, he was terrifyingly large, with wings and a ‘head like
a god’, his lower body ending in a storm and flanked by lions
(Falkenstein, Soden, 137–82).
Numerous goddesses surround Ningirsu in the Lagash pantheon: his
wife Baba, his sisters Nisaba and Nanše and his mother Gatumdug (his
father is Anu. His emblem or alter ego was the lion-headed eagle Anzu/
Imdugud.
The personality of Ningirsu was close to that of Ninurta who replaced
Ningirsu in Akkadian texts of the Old Babylonian period (cf. the myth
of Anzu). They are often mentioned together in god-lists.
Jean 1931, 71–81; Falkenstein, Soden 1953
Read more
here<<<You forgot one possible translation of Ninurta´s name: nin-urta [BARLEY] wr. urta "ear of barley" Akk. antu
That would be lord/lady ear of barley.
Where the names for cities and gods came from will never be known to us,
but it seems unlikely to me that, in Ningirsu´s case, there is a god called lord of girsu (i´m ignoring his female title here) and then people name a city after him.
The other way around has more logic to it.
Ninurta—Sumerian god
His name ‘Lord Earth’ probably derives from the old vegetation-god
Uraš (Jacobsen 1973, 127, suggested ‘Lord Plough’).
He is well known since the Old Sumerian period and closely resembles
the Lagashite god Ningirsu with whom he was eventually identified.
Ninurta instead of Ningirsu features in the Akkadian versions of some
myths (as the one of Anzu from the Old Babylonian period). In Nippur
he was worshipped in the temple E-šumeša. In this city (and in Lagash)
he was called the firstborn son of Enlil, in preference over Nanna, who
was also accorded this title. After the Old Babylonian period, Ninurta’s
popularity waned since Marduk assumed some of his characteristics
(for the precedent of Ninurta’s role in fighting Anzu for the Enuma eliš,
see Lambert, in Hecker, Sommerfeld, 55–60). In Assyria, however, since
late Middle Assyrian times, he was much promoted as a fearsome warrior.
As his name implies, Ninurta was originally an agricultural and rain
deity. The so-called ‘Farmer’s Almanac’, a compilation of the annual
tasks related to the growing of barley, was called the ‘Instructions of
Ninurta’. He was called the ‘farmer of Enlil’ and praised as the ‘lifegiving
semen’, the source of fertility and abundance throughout the
land: ‘you fill the canal, let grow the barley, you fill the pond with carp,
let reed and grass grow in the cranebrake, you fill the forest with game,
let the tamarisk(?) grow in the steppe, you fill the orchard and garden
with honey and wine, cause long life to sprout in the palace’ (Falkenstein,
Soden, 59f). For some reason Ninurta changed from an agrarian god to
the archetypical ‘young god’ or ‘god of wrath’. Several compositions,
mainly from the Neo-Sumerian and Ur III period emphasize this warlike
character of the ‘champion’ (ur.sag) Ninurta: ‘eternal warrior, greatly
respected, with a broad chest, the strength of a lion (…) stepping into
battle (…) the heroic warrior, the right arm of Enlil’ (Sjöberg 1976).
Some of his power derives from the violent floods of springtime; in the
Atra-hasis myth he is the one who opens the dikes (see Flood-myths). A
long and complex bilingual composition is called LUGAL UD
ME.LAM.BI NIR.GÁL, ‘king, storm whose splendour is overwhelming’
(also known as lugal.e). The text manages to reconcile both the fertility
and the martial aspects of the god. The myth describes the time when
irrigation was as yet unknown in Sumer and consequently there was no
agriculture to feed the population. After his victory over the demon,
Ninurta makes a stone wall, a gigantic dike to keep the waters of the
Tigris from flowing eastwards. The result of this labour are fruit-filled
fields and orchards and the kings and gods rejoice. When his mother
Ninlil is impatient to congratulate her son in person and travels to the
hills to find him, he presents her with a vast range he had accumulated
over his enemy’s remains. First, however, he provides the barren stones
with vegetation and wildlife and calls it the hursag; Ninlil herself from
now on becomes Ninhursag. Finally Ninurta decides the fates of the
stones, the former soldiers of Asag. Some are rewarded for having
behaved decently and are given some posts in his administration, others
are punished by curses; an interesting etiological analysis of the properties
of certain minerals (van Dijk 1983). A similar, also bilingual composition
is THE RETURN OF NINURTA TO NIPPUR (or Sum. an-gim dim.ma,
‘created like An’). It begins with a long description of Ninurta’s character
and achievements, especially on the battlefield. He is returning to Nippur
in his chariot which is decorated all over with awe-inspiring trophies,
surrounded by a large and terrifying retinue. The momentum of his
cavalcade threatens the well-being of the country and Nusku, Enlil’s
vizier, tries to persuade the young god to slow down and to dim his
fearsome radiance. He also points out that Enlil will reward him highly
upon his return but that he finds his present style of progress
objectionable. Ninurta does put away his whip and mace, but drives the
rest of the trophies to Nippur. The gods are greatly impressed and even
frightened at the display of booty and his mother, Ninlil, greets him
affectionately. The text ends in a speech of self-glorification by Ninurta,
in which he also refers to his battle with the stones described in lugal.e
(Cooper). Ninurta’s one fault seems to have been arrogance. This is
alluded to in the RETURN TO NIPPUR, and another mythological
fragment tells of an accident in the retrieval of the Tablets of Destiny
(see Anzu-myth). The eaglet (amar-anzu) addresses Ninurta and
complains that because the god had attacked him, he dropped the Tablets
of Destiny into the Apsu. This implies their loss to Ninurta who is
crestfallen. The eaglet accompanies him to the dwelling of Enki in the
Apsu, who receives them in a friendly fashion but does not offer to give
back the Tablets. When Ninurta refuses to leave without them and even
attacks the vizier, Enki fashions a giant turtle out of the Apsu-clay
which attacks the divine hero, biting his toes. Ninurta starts to defend
himself and Enki quickly digs out a pit into which both the god and his
tormentor fall. Only the pleas of Ninurta’s mother Ninmena (Ninlil)
persuade Enki to set him free, by reminding him that he owes her a
favour (Kramer).
Falkenstein, Soden 1953, 59f; van Dijk 1962, 19–32; Sjöberg 1976, 411–26; Cooper
1978; van Dijk 1983; Kramer 1984, 231–7