"The Avari were those Elves who remained content with Middle-earth and refused
the summons of the Powers; but they and their many secret tongues do not
concern this book," Tolkien wrote in an early version of the Appendix on
languages that he was preparing for LotR (PM:29-30). Does this mean that some
Avari deliberately developed or even constructed new languages for the purpose
of secrecy? But some Avarin tongues were evidently similar to the Eldarin ones:
Felagund quickly interpreted the language of the people of Bëor, and one
reason why he was able to do this was that "these Men had long had dealings
with the Dark Elves east of the mountains, and from them had learned much of
their speech; and since all the languages of the Quendi were of one origin, the
language of Bëor and his folk resembled the Elven-tongue in many words and
devices" (Silmarillion ch. 17). Indeed it is said that "in the North and
West of the Old World [Men] learned language direct and fully made from Elves
who befriended them in their infancy and early wanderings" (PM:30), and Faramir
even claimed that "all speech of men in this world is Elvish in descent"
(WR:159, PM:63). In the early days, this Elvish influence on the tongues of Men
could only come from Avarin.
Even the Dwarves seem to have borrowed a few words from the non-Elda Elves, probably long before they met the Eldar in Beleriand. In WJ:391, Tolkien states that "the Dwarvish name for Orcs, Rukhs pl. Rakhâs, seems to show affinity to the Elvish names, and was possibly ultimately derived from Avarin". It is said that in the Avarin tongues (as well as in Eldarin languages), there were many derivatives of the primitive stem RUKU, the source of the Quenya and Sindarin words for "Orc". -WJ:389.
Tolkien's interest lay in the Eldarin branch of the Elvish language family, and it seems that he left the Avarin tongues virtually unexplored. The only actual Avarin forms that are cited in the published material, and very possibly all the Avarin forms Tolkien ever mentioned, are six descendants of primitive kwendî (whence Quenya Quendi) that are listed in WJ:410: Kindi, cuind, hwenti, windan, kinn-lai, penni. (It is said that descendants of primitive kwendî were "frequently found" in Avarin tongues.) These Avarin forms are said to be "cited by the [Eldarin?] Loremasters", who evidently had some scientific interest in the Avarin languages. Each of these forms belongs to a separate Avarin tongue, so there would be six of these languages at the very least, and probably many more (according to WJ:410, the Avarin dialects "were numerous, and often as widely sundered from one another as they were from the Eldarin forms of Elvish speech"). These Avarin words actually did not mean exactly the same as their Quenya cognate Quendi, i.e. "Elves in general". They were the names that the Avari gave to themselves. Notes Tolkien, "They had evidently continued to call themselves *kwendî, 'the People', regarding those who went away [that is, the Eldar] as deserters."
By comparing the forms Tolkien mentions to the primitive form *kwendî we get what may be the only glimpses of Avarin sound-changes that we shall ever have:
- Kindi has lost the w and changed the e to i, perhaps by assimilation to the plural ending -i, that also tells us that the original long final vowels have become short (as in Quenya; cf. also hwenti, penni below).
- Cuind (is it significant that Tolkien uses c instead of k?) has turned the original semi-vowel w into a full vowel u. The original ending has been lost. Is the i just a later form of the original vowel e, or is it a plural infix (perhaps some kind of umlaut caused by the plural ending -î before it was lost?) May the singular be *cund??? (< *kuend < *kwend < kwende?)
- Hwenti shows a change kw > hw and d > t, and the original long final -î has become short -i (as in kindi above and penni below). If hw denotes the same sound as in Quenya (unvoiced w, like English wh in dialects where which is audibly distinct from witch), this hw may be the product of [x] (sc. German ach-Laut) in contact with [w]. Perhaps this branch of Avarin turned the original unvoiced stops into spirants, like [k] > [x], and devoiced the original voiced stops, like [d] > [t].
- Windan has lost the original initial k, turned e into i and apparently strengthened the original -e of the primitive sg. kwende to -a. This Avarin language seems to have introduced a new plural ending -n, not directly descended from the original -î. It is probably derived from the plural element -m that occurred in the primitive language (see LR:360, stem 3Ô). Some of the Quenya cases also show plural -n, e.g. the plural locative ending -ssen; this must also come from primitive -m.
- Kinn-lai may come from an Avarin language closely related to the one that has kindi (above); we note the same change kwe- > ki. Here we also have assimilation nd > nn. The last element lai is certainly not derived from the primitive plural ending -î. Rather it must be related to Quenya lië "people", hence "kinn-people". The stem LI, the source of Quenya lië, may have produced lai by A-infixion (well attested in the primitive language).
- Penni is a form that is singled out as especially interesting by Tolkien. It shows the same change kw > p as in Common Telerin (whence Sindarin and the Telerin of Aman), suggesting "that it had already occurred among the Lindar [Teleri] before the Separation" (WJ:410). Otherwise we see the same assimilation nd > nn as in kinn-lai, while a descendant of the primitive plural ending -î is still present, though it has become short as in kindi and hwenti. Tolkien informs us "the form penni is cited as coming from the 'Wood-elven' speech of the Vale of Anduin". For this reason, some would classify this as a Nandorin word.
Otherwise there is very little. The name of the Dark Elf Eöl, that cannot be analyzed (WJ:320), may be Avarin. It is hinted that Eöl belonged to the Nandor (WJ:322), so this depends on whether we count the Nandor (Green-elves) as Avari or not.
It is said that though the original clans were still remembered among the Avari, "there is no record of their using the name Ñoldo [that is, any direct descendant of primitive ñgolodô] in any recognizable Avarin form" (WJ:381).
Those who wish to engage in "fan fiction" can start constructing the Avarin languages that the words Kindi, Cuind etc. belong to, deriving them from Tolkien's Primitive Quendian.