Welcome Tahir bhai.
You wrote: “Do you mean Nada = Azan?” .... Do you mean Day of Jumua = sixth day of the seven day week? Was there a day of week called Jumua in 6th century Arabia? Do you remember the fairy tale about how the ritual of azan was agreed upon? Any bells ringing in your mind?”
The word from root ن د و itself means: moist; proclamation; Call; summon; call out to someone; meetings; etc. One has to determine its meanings in the context in which this word is used. For example, in 20:11 Moses is called through a loud voice with his name, O’ Musa, similarly in 79:16, etc. When this is used in 62:9, it clearly establishes the following points. (i) there was a fixed day of week for congregational prayer, (ii) people were called through loud voice/call to come for salat, and (iii) the call had some specific words to call with.
Quran does not say “Al-salat ul Juma’ “, rather it says, “al-salatu min yaum il jumma’ = the salat on the day of congregation.” Thus, it is obvious there was a fixed day during the prophet’s time on which people used to gather to pray and that this day was known as “the day of congregation.” This must have been a fixed day, only then the word “yaum = day” can be appended next to it. This fixed day must have been one of the seven days of the week. Due to its regular usage, they subsequently started calling that day as “Jumma’.” Allama Parwez in his lughat mentions that day was called “Aruba” which was subsequently named by Ka’eb bin Lui as Yaum ul Jumma’.
Since 62:9 does not give any indication about the form of this call for salat, it left open a way for prophet to come up with the words for such a call and the mode/manner of delivering this call. Prophet settled on certain specific words/phrases and the method to do so. It does not matter if this was called Adhan back then or was given this specific name later. My understanding is that since it is a specific call for a specific purpose with specific words/phrases and a specific manner of delivery, it is unique in that sense, thus, they came up with a unique name “adhan.” Thus, the word Adhan is associated with the call for prayers and nothing else.
Yes, I do recall something about how they might have arrived at finalizing the Adhan. To me, this is a non-issue. Even if those fairy tales are partially true, they impart a lesson for us, that is, prophet consulted his companions for matters not fully settled and communicated to him by God.