Quendi and Eldar
Quendi and Eldar is a collection of short essays by J.R.R. Tolkien dating from c. 1959-60, which were published in The War of the Jewels. Quendi and Eldar provides the etymological development of certain words the Elves used to name themselves and other peoples, or to refer to individuals in some way.
A large section of "Appendix D. *Kwen, Quenya, and the Elvish (especially Ñoldorin) words for 'Language'" was omitted from The War of the Jewels, and was released years later in Vinyar Tengwar, Issue 39 together with a shorter text entitled "Appendix: Noldorin words for Language".