Who is Dhun-Nun?

Salaamun alaykum!

Dhun-Nun is another prophet whose identity has been misinterpreted in the books of tafseer. This makes think that even the meaning of "nun" might have been added later in the dictionaries to indicate "fish" or "whale" just because the mufasiroon thought Dhun-Nun is Yunus (whose story seems distorted too).

Actually, the Qur'an tells us a different story. Let's first analyze the only two ayaat in surah al-Anbiya that talk about Dhun-Nun:

وَذَا ٱلنُّونِ إِذ ذَّهَبَ مُغَٰضِبٗا فَظَنَّ أَن لَّن نَّقۡدِرَ عَلَيۡهِ فَنَادَىٰ فِي ٱلظُّلُمَٰتِ أَن لَّآ إِلَٰهَ إِلَّآ أَنتَ سُبۡحَٰنَكَ إِنِّي كُنتُ مِنَ ٱلظَّٰلِمِينَ (87)

فَٱسۡتَجَبۡنَا لَهُۥ وَنَجَّيۡنَٰهُ مِنَ ٱلۡغَمِّۚ وَكَذَٰلِكَ نُـۨجِي ٱلۡمُؤۡمِنِينَ (88)

(Pickthall's translation)

"And (mention) Dhu'n-Nun, when he went off in anger and deemed that We had no power over him, but he cried out in the darkness, saying: There is no Allah save Thee. Be Thou Glorified! Lo! I have been a wrong-doer." (87)

"Then we heard his prayer and saved him from the anguish. Thus we save believers." (88)

From these ayaat, we extract the following information:

1.Dhun-Nun must be a descriptive name related to something called "nun", which must necessarily be relevant to his story.
2. He is characterized by anger and impatience.
3.He did something wrong and fell into a state of "dhulumaat" which denotes he fell into a state of darkness and blindness, as Allah describes:

وَمَا یَسۡتَوِی ٱلۡأَعۡمَىٰ وَٱلۡبَصِیرُ (19) وَلَا ٱلظُّلُمَـٰتُ وَلَا ٱلنُّورُ (20)

ٱللَّهُ وَلِیُّ ٱلَّذِینَ ءَامَنُوا۟ یُخۡرِجُهُم مِّنَ ٱلظُّلُمَـٰتِ إِلَى ٱلنُّورِۖ وَٱلَّذِینَ كَفَرُوۤا۟ أَوۡلِیَاۤؤُهُمُ ٱلطَّـٰغُوتُ یُخۡرِجُونَهُم مِّنَ ٱلنُّورِ إِلَى ٱلظُّلُمَـٰتِۗ ... (2:257)

4. He realized the gravity of his wrongdoing and repented.
5. Allah responded to his prayer and delivered him from that darkness and anguish (gham).
6. Allah testifies he is a believer (mu'min).

Perhaps, these hints may remind you of someone, but we need to find some markings. The following words were the ones that led me to seriously think of a particular prophet:

1. Word مغاضب of root verb غضب (to be angry, irritated, furious).

It indicates Dhun-Nun is hot-tempered and impetuous. Who else is like him? Interestingly, besides Dhun-Nun, the only person I found related to the word غضب was Musa. Allah tells us he came back to his people غضبان:
وَلَمَّا رَجَعَ مُوسَىٰۤ إِلَىٰ قَوۡمِهِۦ غَضۡبَـٰنَ أَسِفࣰا...(7:150)

فَرَجَعَ مُوسَىٰۤ إِلَىٰ قَوۡمِهِۦ غَضۡبَـٰنَ أَسِفࣰاۚ... (20:86)

In addition, in surah al-Kahf, we also find Musa impatient:
قَالَ أَلَمۡ أَقُلۡ إِنَّكَ لَن تَسۡتَطِیعَ مَعِیَ صَبۡرࣰا (18:72)

سَأُنَبِّئُكَ بِتَأۡوِیلِ مَا لَمۡ تَسۡتَطِع عَّلَیۡهِ صَبۡرًا (18:78)

2. Word الغم (anguish, agony).

The only individuals Allah mentions to have delivered from al-gham in particular are Dhun-Nun and Musa:

Dhun-Nun (21:88): فَٱسۡتَجَبۡنَا لَهُۥ وَنَجَّيۡنَٰهُ مِنَ ٱلۡغَمِّۚ
Musa (20:40): وَقَتَلۡتَ نَفۡسࣰا فَنَجَّیۡنَـٰكَ مِنَ ٱلۡغَمِّ

So, we find out that Dhun-Nun may be Musa and his sin was about the killing of a man.

Such crime made Dhun-Nun fall into a state of "dhulumaat" which also represents the dark state of loss and distress caused by shaytan:

فَنَادَىٰ فِي ٱلظُّلُمَٰتِ أَن لَّآ إِلَٰهَ إِلَّآ أَنتَ سُبۡحَٰنَكَ إِنِّي كُنتُ مِنَ ٱلظَّٰلِمِينَ

This corresponds with what Musa said in 28:15-16: after the incident of killing:   
                   
قَالَ هَـٰذَا مِنۡ عَمَلِ ٱلشَّیۡطَـٰنِۖ إِنَّهُۥ عَدُوࣱّ مُّضِلࣱّ مُّبِینࣱ (15) قَالَ رَبِّ إِنِّی ظَلَمۡتُ نَفۡسِی فَٱغۡفِرۡ لِی فَغَفَرَ لَهُۥۤۚ إِنَّهُۥ هُوَ ٱلۡغَفُورُ ٱلرَّحِیمُ (16)

So, they both repented and were answered by Allah.

3. Allah testifies Dhun-Nun is a mu'min: وَكَذَٰلِكَ نُـۨجِي ٱلۡمُؤۡمِنِينَ

Also, Musa is mentioned to have said:
قَالَ سُبۡحَٰنَكَ تُبۡتُ إِلَيۡكَ وَأَنَا۠ أَوَّلُ ٱلۡمُؤۡمِنِينَ (7:143)

4. What about "nun"? Why is he called Dhun-Nun and how is "nun" related to the story of Musa?

Let's read how Allah SWT describes the scene in surah al-Qasas:

وَدَخَلَ ٱلۡمَدِینَةَ عَلَىٰ حِینِ غَفۡلَةࣲ مِّنۡ أَهۡلِهَا فَوَجَدَ فِیهَا رَجُلَیۡنِ یَقۡتَتِلَانِ هَـٰذَا مِن شِیعَتِهِۦ وَهَـٰذَا مِنۡ عَدُوِّهِۦۖ فَٱسۡتَغَـٰثَهُ ٱلَّذِی مِن شِیعَتِهِۦ عَلَى ٱلَّذِی مِنۡ عَدُوِّهِۦ فَوَكَزَهُۥ مُوسَىٰ فَقَضَىٰ عَلَیۡهِۖ قَالَ هَـٰذَا مِنۡ عَمَلِ ٱلشَّیۡطَـٰنِۖ إِنَّهُۥ عَدُوࣱّ مُّضِلࣱّ مُّبِینࣱ (15) قَالَ رَبِّ إِنِّی ظَلَمۡتُ نَفۡسِی فَٱغۡفِرۡ لِی فَغَفَرَ لَهُۥۤۚ إِنَّهُۥ هُوَ ٱلۡغَفُورُ ٱلرَّحِیمُ (16)

The word used to describe the way Musa killed the man is وَكَزَ, which means "to pierce, stab".

In the old dictionary of Ismail bin Hammad al Jawhari ,"Lughah wa Sihah al-Arabiyah", 1003 CE, "nun" appears to mean "sword-blade", and it was a type of sword or knife for some Arabs. If you check online for the old Arabian swords, you will find النون (nun) in the list.

Thus, the name "Dhun-Nun" becomes relevant to Musa's story.

FOOD FOR THOUGHT
The Sign of "Nun"

I cannot miss and ignore an interesting sign that keeps flashing in 21:88, within the story of Dhun-Nun:
وَكَذَٰلِكَ نُـۨجِي ٱلۡمُؤۡمِنِينَ

Despite being written without ن, the word نُـۨجِي is holding a second ن only in recitation. What is the history behind it?

In the Uthmani rasm of the mus'haf, that word has only one nun and is written "نُـجِي". This is a word which different qira'aat read it with two ن as نُـۨجِي , and others with only one.
Then, the mus'haf was written with only one "nun", and a small ن was written in by later scholars for those reading in the qira'aat which use two.

In the riwayah of Hafs, we read the word with two ن, and thus the small one is written in the copies of the Qur'an meant for reading the way of Hafs.

My question is: Since originally that word is written without the second ن, and other qira'aat do not pronounce it, what is the real meaning of the verb نُـجِي? Could it indicate another supplementary meaning pertaining to Dhun-Nun and thus proving another marking that might relate to Musa?

Here, we need a hand from an expert of Arabic to find out the exact word root of نُـجِي.

It would be fantastic if we find out the word "nun" exists in any of the hyerogliphic inscriptions as a weapon used in ancient Egypt. And that would clarify many more things!!! 

Allah knows best!