Do we happen to have any idea how many Noldor came to Beleriand, either by crossing the Helcaraxe or by the stolen ships? asking for Reasons.
This essay attempts to find some reasonable numbers for how many elves there are at a given time, figuring based on “some guestimate of the largest possible population of Noldor in Aman which might not require the wholesale slaughter of Orome’s hunting stock just to feed the masses.” I love that quote.
He comes to about 70,000 crossing the Helcaraxe and about 25,000 taking the ships, yielding less than 100,000 arriving in Beleriand.
The numbers Michael Martinez comes up with feel really big, which is an objection he anticipates -- and his logic seems perfectly sound to me. However, I have time on my hands and a burning fever so I’m going to work backwards from the ten thousand troops Turgon shows up to the Nirnaeth Arnoediad with (because I always prefer to work backwards from Turgon).
So let’s assume that Turgon’s total fighting force is somewhat less than half of his people. I figure this because, while the vast majority of the Noldor who followed Fingolfin would have acquired at least shooting and seal-clubbing skills, it seems that Fingon was the family’s warrior and Turgon was responsible for preserving Noldorin culture in peace and secret, so he probably got the lion’s share of noncombatants regardless of how much you think Fingon knew about Gondolin. Also, more children would have been born in Gondolin than elsewhere, given the Noldor’s customs about childbearing in time of war. Here’s where I differ from Martinez: I’m figuring Turgon brought almost his full strength to an alliance of such import as the Nirnaeth -- it’s secrecy that protects Gondolin, not force. But -- and here’s that almost -- given that he left his heir behind in case he fell, he would undoubtedly have left Maeglin an honor guard at the very least -- and Turgon is too practical and loves his city too much to leave the very least.
So if Turgon’s 10,000 is a bit less than half of the city’s population, let’s give him (for the sake of round numbers) 25,000 total. Working backwards (to account for breeding), let’s give him 20,000 who left Nevrast for Gondolin -- but wait! We know that not all of Gondolin’s lords were Noldor, and presumably not all of their people were! Rog is widely thought to have been non-Noldor (mostly because of the name; his name is the sole reason he got left out of the published Silmarillion, actually) and Galdor’s description suggests the Laiquendi. I, personally, really like the idea of Gondolin as a very cosmopolitan and multicultural city, with the rewards and tensions that implies, so let’s go with that. So (farewell, round numbers) let’s give him 18,000 Noldor per se, 2,000 additional elves, who go to Gondolin.
The Noldor that Turgon took to Gondolin were a third of Fingolfin’s people, so let’s make the Nolofinwean group number 54,000. Martinez suggests that Fingolfin had about twice as many in his company as Feanor did, while Finarfin’s sons took about as many people as Feanor with them, which I find reasonable. So -- and we’re back to Martinez’ number. About 108,000.
Again, though, that’s ... a lot of elves. I think most of us tend to conceive of Beleriand as a smaller world.
And wait! We have linguistic evidence that big round numbers that sound nice tend to become part of household speech for elves -- Menegroth is called “the thousand caves” (or the 1758 caves? I don’t really grok base-12). Do we believe that it was exactly 1000 caves and no one was ever allowed to build on or remodel lest they have to change the city’s name? I don’t. Could Turgon’s force of ten thousand be a “forty days and forty nights” situation, where this is cultural shorthand for “a whole bunch”? That would certainly match how Tolkien’s narrative voice usually handles numbers, in hosts and companies and manies. Maybe that force of ten thousand is more like 7,859. Maybe it’s more like four thousand. Especially given that we may, depending on which canon you’re reading, be translating from base-12 numbers to base-10 numbers (again, understanding that is quite beyond me), with accompanying uncertainties in either direction.
Personally, my (rather extreme) preference is to lop a zero off any number Tolkien gives. I enjoy the tension between exaggerated-for-effect-until-it-came-to-sound-like-truth tens of thousands and a smaller, more desperate reality. I call it a magnifying series of roundings-up for ease and effect on the part of the literary agents for each book, which survive because they feel epic enough -- so that I get a smaller, more intimate population to work with in fic, casting this ten-times-larger shadow. Handily, this lets me just do my calculations over without a calculator -- Turgon brings 1,000 to the Nirnaeth, Gondolin’s population is 2500 total, giving us roughly 6000 under Fingolfin, 3000 under Orodreth, 3000 under the Brothers Feanorian -- and 12,000 total Noldor arriving in Beleriand. (For interest’s sake, this means that, say, Doriath can’t have a population of fewer than about 15,000 in order for the local elves to significantly outnumber the Noldor.)
So, depending on your Reasons, I think any number of Noldor arriving in Beleriand between 12,000 and 110,000 is perfectly reasonable and shouldn’t raise a whole lot of eyebrows.