Doriathrin

Doriathrin is a language (or dialect) devised by J.R.R. Tolkien.

Originally it was the language of Doriath, which was only losely related to the Ilkorin tongue, i.e. the language of the other Elves of Beleriand. But as Tolkien later changed his conceptions regarding the names and interrelations of his languages and their speakers it became only a dialect of Sindarin (which now took the place as the Beleriandic language. Thus it is unclear whether the Doriathrin of the Etymologies is the same as that of the post LotR period.

Doriathrin in the Etymologies
The Doriathrin of the Etymologies differs from the Welsh-sounding language (then called Noldorin, later Sindarin) in several aspects.


 * Grammatical aspects
 * The plural is generally marked by suffix -in, while in Noldorin we normally find vowel changes and only very few cases of -in (which might be a borrowing). This might consists of the old plural endings -î (as in Quenya and originally in Sindarin (later only observable in the vowel changes it triggered) and -m (as sometimes in Quenya).
 * The gentive is in the singular marked by the suffix -a(n), which we find in the word Nauglamîr (originally naugla mîr, lit. 'dwarf's jewel'), in the plural by -ion (as in Quenya), which both do not occur in Noldorin (where the singular was originally ('Old Noldorin') marked by -en, which was later lost).
 * Phonetic aspects
 * Quite unlike Noldorin we do not find any i-affection in Doriathrin. I.e. while old urkô, pl. urkî(m) changed to Noldorin orch, pl. yrch we find urch, pl. urchin in Doriathrin.
 * Then there are some minor differences, like not shifting archaic u to o (as is sometimes found in Noldorin also), some missing lenitions, change of archaic â to ô rather then to au (as in Noldorin) and the like.

Doriath-Sindarin
The Sindarin dialect of Doriath in Tolkien's post-LotR conceptions is much poorer attested. In fact we basically only know that it was more archaic than the other dialects and that it did still use genitive -a, as we see on the tombstone of Túrin (Dagnir Glaurunga, 'Slayer of Glaurung') and in the still occuring name Nauglamîr.

Summing up
So we do know that one grammatical aspect of Etymologies-Doriathrin did survive into Doriath-Sindarin, and this very aspect (namely suffix -a) is now completely in accordance with Sindarin, since in Old Sindarin the genitive was no longer marked by -en, -ion, but by -o. This is regularly lost in normal Sindarin, but might survive as -a in the dialect of Doriath. Other aspects as the mentioned phonetic differences between Etymologies-Doriathrin and Noldorin might be regarded as dialectal, so it does not seem unlikely, that we might in fact regard the Doriathrin vocabulary of the Etymologies as still existant in later Doriath-Sindarin.