In regard to the purpose of this thread, its purpose is to discuss any and all aspects of EQ and the elven language contained within its pages. So yes, it will include specific language mechanics found within EQ as the basis for fleshing out all the missing parts of the language.
It seems we agree about the Go-Backs and how specific elf tribes will most likely have a more diverse vocabulary for specific things. As you mention the "white cold" and the "death sleep" I started thinking about Cutter's wolf "War Frost." This name might imply the Wolfriders already had the name for frost (and I'm assuming they would as frost is even more common than snow). However, the Wolfriders did not know the word "war" until Rayek informed them of its meaning in Book 4 (just prior to the war with the trolls). Not terribly important, just interesting how the chronology of naming wolves follows this idea of varying lexicons between tribes.
I think your idea of the "primal" language is interesting and probably accurate (as all further language by all elves, trolls and preservers was based off of this). But yes, function is important for names, regardless of species. For example, FRAK (defined as a fracture, crack, break, etc.) is perfect for a troll but not perfect (probably) for an elf. However, during the Rebel series we hear one of the soldiers say something along the lines of "this computer is all frakked up." So, it seems that this word shifted to human speech though its roots seem to have been lost with the original elf language. I say this because Jink, when holding the small palace, exclaims "High Ones" in a language that is familiar to her but she doesn't know what it means (I'm probably not explaining the scene accurately, but its the basic idea). So, Jink seems to speak only human at that point in time.
I would agree with you about accents. Thought I have studied linguistics quite a bit I have not studied much on how accents develop (or how "pigeon" or argotic languages are developed). Fascinating stuff. An interesting study was done on Gulla Gulla Island but I can't find the specific one I am thinking of. I read it back as an undergrad (which seems like a lifetime ago). You make a very valid point with the idea that those elf tribes with older members (such as Savah) would more likely have a more "original" dialect than those elf tribes whose members have much shorter life spans for various reasons (Wolfriders and Go-Backs). I'll have to add this to my notes. While focusing so much on language mechanics I have given little thought to dialects. We'll call what I am developing "Standard Elvish" or something similar. Perhaps later there will be different dialects. I had problems with this type of thing with Arabic. I learned "Standard Arabic" which everyone could understand. The people I communicated with did not speak in "Standard Arabic" however so I had a hard time understanding them. Frequently this made for very one-way communication. Elves can always "send" and I'm assuming this is not done through..."verbal" messages. What I mean by this is that they didn't send thoughts with language, but with images and emotions. I can find quotes about what I mean if this is unclear.
As for your statement about the elven language being nearly impossible for humans to pick up, I'd have to respectfully disagree. In my experience, language is language. The reason I believe elves speak "human" so much better is that they frequently observe humans while remaining undetected. Almost never do the humans observe elves...either detected or not. So, there is little chance for humans to learn the elven language. Also, humans have a more reduced lifetime so a more narrow window to learn the language. If an elf learned even one human word a year they would amass a considerable vocabulary by the end of their life (information which could then, potentially, be passed on to other elves). Tyleet's adopted son, Patch, spoke elvish fluently (makes me wonder if he had an accent while speaking "human"). Another interesting thing is that Cutter seems fluent in "human" during the era of the first holt and then his understanding and ability to speak the language is significantly reduced during Shuna's era. It seems the human language developed and shifted and Cutter wasn't able to keep up (possibly because he was sleeping in "wrap-stuff").
It's a fine point to argue either way and I think some explanation of this will have to be prepared for the final manual. It even has me scratching my head (probably why I am going bald).
Great questions and points, Trollhammer. Discussing this has been very enjoyable. I look forward to more discussions with you in the near future. All the best.