dingir (𒀭)... or TINGGIR

In Sumerian AN (𒀭), which is also dingir (𒀭), means variously "heaven, sky, star" and forms a portion of the name of the father of the gods ANU (𒀭𒀭). It can be used as a determiner prefixed to words, which is silent when read aloud in the words it is affixed to.

Where did #dingir (𒀭) come from? Is it part of the hypothetical "linguistic substrate theory" of Sumerian?

I’d say that linguistic substrate is from the Austronesians.

In Malay:

#tinggi means “#height, #high, #lofty, #tall”.

#tinggil means “royal terrace”, typically a place where nobility present themselves to their subjects, looking down upon them from an elevated position.

#tinggal means “to live; to leave; to stay behind; to be left; remaining over or behind, abiding in a place; left over; left behind; remaining in a place; residing”

#tinggali or #tinggalkan: “to forsake; to abandon; to leave behind”

d =t

i = i

ng = ngg

i = a/i

r = l

#Dingir is written with #AN (𒀭) “#heaven”, “#sky, #star”

Austronesians sailed by the stars on the ocean, which is a reflection of the sky where a thousand islands are reflections of thousands of stars. They had / have a highly sophisticated indigenous astronomical and calendaring system, which you don’t accidentally acquire.

Being that the earliest elements of Mesopotamian religion revolve around water and the sea, sea monsters and all manner of maritime absurdities, I’d say their religion came from a maritime people. Especially the mythology regarding Enki, Tiamat, and Apsu.

Furthermore, I’d say that the gods were not in the least bit divine, but were deified ancestors who survived a great cataclysmic event.

Indonesian, also has very much the same linguistic elements. I venture that they are even more clearly connected to the Sumerian dingir (𒀭):

tinggal: “to stay, rest; to live; to remain, remaining, left (behind/over), stay around (after everyone else has left); to stop, finish; left back; neglected, ignored”

tinggi: “high, tall; height, level, altitude; old; near the zenith (of the sun); #advanced, #higher (of civilization, education, age, etc.), high-ranking (of one's position)”

#tinggir / #ténggér / #Ténggér: “a perch”; “an ethnic group which lives on the slopes of Mt. Bromo in East Java”

Mountains are a great place to observe the innumerable stars…

And "innumerable" is exactly what TINI / TINGI / KINGI means in Polynesia.