Sorry for a very long reply, guys. You've asked some very complicated philosophical questions, OP, so it will take much space to make my thoughts more clear to you. The direct answers are below there, but I guess you won't be satisfied with them unless you read the way of my thoughts. I hope you'll find this reply interesting and it could lead you to some other thoughts which could bring us some new views on the topic. Thanks for reading!

One of the reasons I like the ES universe is that sometimes it gives absolutely exact definitions of different events but names them the way which makes people misunderstand them . You remember our talks with Sotha Sil? He called us the Prisoners and answering our question of what did it mean, he gave the exact features of a video game player. Ok, here we have two questions: where did the Elder Scrolls come from and what is the earliest chronological mention of the Elder Scrolls. To answer these questions we first need to understand the definition of an Elder Scroll we all know: an Elder Scroll is an artifact of an unknown origin and quantity, being simultaneously an archive of some historic, past and future events. They often tell of events that require a Hero to resolve them, although the Scrolls themselves do not select such individuals. A Hero, in most cases, from the outer world whom Sotha Sil also called the "Prisoner" - us. The Elder Scroll's of Mnem protector Arfire said that many believe the Elder Scrolls were created by the Aedra, but why or when is unknown.

So here is a brief summary. The Elder Scrolls:
1. Have never been existing and have always been existing the same time;
2. Have been written by the Aedra (or have been simply existing along) with some unknown purposes;
3. Until the events each Scroll describes comes to pass, they contain information about possible events in the future, with each viewing containing a possible version of events (read the Divining the Elder Scrolls);
4. Once a prophecy contained in an Elder Scroll is enacted in Tamriel, the text of the parchment becomes fixed. After that time, all readers ingest the same divine message, creating a historical document declaring the unequivocal truth of a past event. The contents of a scroll, once solidified, cannot be altered by any known magic (Lost Histories of Tamriel);
5. Events which alter the linearity of time, such as the Dragon Breaks, cannot be recorded or predicted by the Elder Scroll (read the Where Were You When the Dragon Broke?).

Well, we could stop it here, but to make it more clear:
6. Nirn was created by the local gods, the Aedra, who left it's creation. Julianos, Dibella, Mara, etc. It is not a secret that those Aedra are actually the game designers, programmers and beta-testers of almost the same names. So, now I think that the belief "the Elder Scrolls were created by the Aedra" gains some other, more real understanding because..
7. There are 13 known to us Elder Scrolls with only 6 of them seen in Cyrodiil. There are 13 full Elder Scrolls games (Arena, Daggerfall, Battlespire, Redguard, Morrowind, Stormhold, Dawnstar, Shadowkey (yes, these three are separate games) Oblivion, Skyrim, ESO, Legends and Blades, not counting the DLCs) - each of them is called the Elder Scrolls . Moreover, there were only 6 games by the time of TES IV: Oblivion, which took place in Cyrodiil - we have exactly 6 Elder Scrolls to fight for in Cyrodiil in the ESO today. The total number of the Elder Scrolls games is unknown because only the future shows it to us, it is the matter of time.
8. Finally for now, an example regarding Time to answer your questions above. Keeping in mind Sotha Sil's "Prisoner" concept, I met Vivec in 3E 427. That was the first time I spoke to him from my Prisoner's perspective, but that was our second meeting actually, because from his perspective, the first time we met happened in 2E 582 during the current ESO events. I came to help him in 2E 582 only because I knew of the "future" events to come in 741 years! That would be very cool if Vivec told me something like "Though I will not discuss the prophecy of the Incarnate, I know you, because you saved me hundrends of years ago during a war in the West.", but he lacks that dialogue line in 3E 427 .. It's much of the "Last Thursdayism" theory here, but it works within the concept of two worlds, the virtual and the real ones. Nirn simply did not exist before 3E 389, the year TES I: Arena began.

You've read the article on the Elder Scrolls on the UESP - read it again, keeping in mind that it describes not only the in-game and lore items, but the Elder Scrolls games themselves from the same in-game perspective. TES games are all so close to breaking the fourth wall, but they never do it. Everything within a closed-loop system must stay within it. So it is not only the concept of a videogame player existing within the game itself, it is the game itself being represented as a certain scroll, an item, within itself.

So:
Where did the Elder Scrolls come from? - they are created by the Aedra. The Elder Scrolls are both parts of Nirn and are Nirn itself. Hmm, I guess a smart Daedra Lord willing to destroy Nirn should have tried to seek out an option to rewrite, change or destroy exactly the Elder Scrolls instead of taking Towers, commiting the Soulburst, ravaging tamrielic lands or something . But none of them even thinks about it, though they surely must be aware of the Elder Scrolls nature and of what threat it poses to them.
What is the earliest chronological mention of the Elder Scrolls? - depends on what chronology you mean. Basically, it happened in 3E 389 when Blubamka asked us to retrieve a parchment which held within its writings clues to decipher the part of the Elder Scrolls - that was the first mention, as far as I know, it happened on the "pages" of the TES I: Arena events. Otherwise, it is the Prophet , 2E 582. Regarding books: I think it's not possible to date those books mentioning the Elder Scrolls today, so they can't be counted dependable within the matters of chronology.