Here is my theory: NTR = NT + R = Nut (heavens) + Ra (sun).

What I did was first I looked at the phonetics and meaning of the word "God" in other major cultures of Egypt's time: Sumeria, the Proto-Turkics, the Indo-Europeans, and the Chinese. Their words were Dingir, Tengri, Dyeus, and Tien, respectively. Each of these terms tends to have a common phonology of D/T, I/E, and N, and they also have "heaven" as a secondary meaning. And in the case of the first three there is a meaning of day, sky, brightness, or shinyness. Scholars sometimes even connect these words. See for example Wikipedia's entry on Tengri for a bit of information on that.

Turning to Egypt, we find that the word for god, NTR, contains similar phonetics to those other religions' words for god. So then I looked at which gods start with N and might line up with this phonetic pattern and whether they are associated with the same secondary meanings (heavens, day, etc.)

And there amongst the Egyptian gods we find the primordial waters Nu with his consort Nunet, who represents the primordial waters that are in the heavens. We also find the heavens goddess Nut and the warrior/weaver goddess Neith. Each of these three goddesses is closely associated or equated with the heavens, particularly with the sky cow goddess of the celestial waters, Mehet-Weret, meaning Great Flood. "Great Flood" and the heavens are also equated with Hathor, meaning the "House of Horus", referring at least in part to the belief that Hathor is Horus' consort or mother. Considering that Horus("the Falcon") is associated or equated with Ra, this implicitly suggests that Nut or Neith are practically also a kind of house of Ra or Horus. In Egyptian mythology, each day Ra (and Horus as a form of Ra) go through the sky and into Nut's mouth, to be reborn the next day.

Thus we find in Nut/Neith/Nunet both the kind of phonetics we are looking for, as well as the concept of the heavens that we find in those other religions. The concept of the celestial waters is actually not so strange for ancient mythology and can be found in the division of the waters in Genesis as well as in Babylonian mythology.

It's interesting to me that the Sumerian sign for Dingir looks a bit like it has arrows combined together, and that the symbol for Neith is also arrows and a bow combined.

But where in my theory are the god of the day, shinyness, and brightness? The Dingir sign is commonly drawn as a star, so what is the star here? And where is the R in NTR?
Here is where Ra and Horus, who is an aspect of Ra - Ra on the horizon - come in.

As Sir Ernest Alfred Wallis Budge writes on p. 218 of The Gods of the Egyptians: Or, Studies in Egyptian Mythology, Volume 1, Ra is the God of Day. Ra as the sun is the nearest star to earth and he shines brightness. Here is the R we have been looking for.

Bear in mind also that Horus (in Egyptian Hor, the falcon) is considered the god of light, and that Horus is closely associated or equated with Ra. In fact, both Horus (the falcon) and Ra are commonly depicted as having falcon heads.
(On Horus as god of light, see: Encyclopædia of Religion and Ethics, - Page 64, James Hastings, ‎John Alexander Selbie, ‎Louis Herbert Gray - 1916 )

The "Ancient Egypt Online" website explains in its article on Ra:
"As the king and leader of Egypt, the pharaoh was seen as the human manifestation of Horus, so the two gods (Ra and Horus) became connected. This new deity fusion was then referred to as “Ra-Horakhty” meaning Ra is Horus of the Horizon."


Thus we can see a connection between Nut/Neith, Ra and NTR not only by A) looking at the phonetics and meaning of god in other ancient cultures and theorizing that NTR must mean something similar, but by B) see the phonetic resemblance to NTR in both Nut/Neith and Ra, and by C) seeing how Nut/Neith and Ra have meanings that line up with the names of god in those other cultures.


How can we put Ra together with Nut and get NTR?
There are several ways conceptually to do this in Egyptian mythology's way of thinking. First, consider as I mentioned earlier that Hathor, who is de facto the goddess Nut/Neith, means "house of Horus". Conceptually, Ra/Horus go inside and combine with Nut/Neith every day.

Secondly, consider that Egypt had a practice of combining gods and, consequently, their names to conceptualize a god that was both of them. In this way, Amun + Ra = Amun-Ra.

Third, you may ask how a combined god could be both male and female, as in Nut/Neith + Ra. Consider that Neith herself was sometimes shown as having a phallus and that a few deities were portrayed as having both male and female parts, reflecting their roles as auto-pro-creative.

The Tour Egypt website describes this male, creative aspect of Neith in its essay on Neith:

"She was called 'Nit, the Cow Who Gave Birth to Ra' as one of her titles. The evil serpent Apep, enemy of Ra, was believed to have been created when Nit spat into the waters of Nun, her spittle turning into the giant snake. As a creatrix, though, her name was written using the hieroglyph of an ejaculating phallus - - a strong link to the male creative force a hint as to her part in the creation of the universe. According to the Iunyt (Esna) cosmology the goddess emerged from the primeval waters to create the world. "


What do you think about my theory?