Meaning of son of nun

(Joshua son of Nun) is the servant of Moses. He is also the successor of Moses (as Jews say) and has a book in the Bible bearing his name (book of Joshua).

 Ancient Israelites at the time of Moses (and a maybe a century or so after) knew the meaning of the name (son of nun) or as it in Hebrew (ben nun). Because they still remember the story (or the incident) that caused the name.

 Few centuries after Moses, people forgot the story, therefore became ignorant about the meaning of the name (son of nun). So they misunderstood it and considered (nun) to be a man (I.e. father of Joshua)[1]. Early Muslim scholars in general (who came later, like al-Ṭabarī and others), also followed that Jewish understanding.

Original meaning of the name (ben nun)

 In Semitic languages, like Arabic[2], Aramaic and Assyrian[3], as well as Hebrew[4], the word (nun) means (fish).

A mythical Talmudic story[5] was invented later [borrowed from the story of Jonah (Yunus) or (dhu an nun, as Quran called him)] linking Joshua to a fish (nun) that swallowed him.

The invented myth, contains some shadow of the truth. It says that Joshua is ignorant[6] of his origin, and a fish (nun) swallowed him. This myth is like implying that (nun) is NOT the name of the father[7] of Joshua. Also seems to imply that when people called him (son of nun) they originally meant: son of that fish (which swallowed him). Still with the invented myth, Jews cannot remember the real forgotten story (incident).

Quran is bringing back the forgotten story

60. And (remember) when Musa (Moses) said to his boy-servant: "I will not give up (travelling) until I reach the junction of the two seas …. / 61. But when they reached the junction of the two seas, they forgot their fish, …./ 62. So when they had passed further on, Musa (Moses) said to his boy-servant: "Bring us our morning meal; …. / 63. He said:"Do you remember when we betook ourselves to the rock? I indeed forgot the fish, … [Surah Al-Kahf (The Cave)].

The (nun) then, is (the fish forgotten by the boy of Moses). (nun) is NOT the name of a man (father of Joshua), and (nun) is not a fish swallowed him (like Jonah), but (nun) is the LUNCH (fish) forgotten by the boy-servant near the rock.

 The ancient Israelites knew that incident (of the boy and the running away fish), and because of that strange incident, they called the boy of Moses by the title "son of fish" or as in their tongue (ben nun) or (son of nun). They meant by the (nun) the lost fish which was carried by the boy during the journey (so later, Moses and his boy will eat it when both get hungry).

 Ancient people (especially Semites) usually prefer to name a person after[8] something he did or happened to him, they will call him (son of that deed or that something).Early Arabs use that a lot, and best example is in Quran: (ibn as sabeel) or (son of the road). In the same manner, early Israelites linked that boy to the fish (lunch/meal/food) he forgot and lost.

Then over the centuries, the story was forgotten. Only the famous title (son of nun), was transmitted by tongues generation after generation, and remained in Jewish memory. The scribes who came very late got confused and thought that the name "nun" was the name of a man (father of Joshua), and they recorded it in biblical text as such.