While some features of Elven grammar go back to the earliest records, such as the “Qenya Lexicon”, others are unique to later works such as the “Secret Vice” poems and the Etymologies, and some do not emerge until after The Lord of the Rings. The Elven languages form an expanding canvas (like Niggle’s), and many of the individual poems and sentences can be examined in terms of how they elaborate or enhance the overall grammar of Elvish.
Gilson, Christopher and Wynne, Patrick
"The Growth of Grammar in the Elven Tongues,"
Mythlore: A Journal of J.R.R. Tolkien, C.S. Lewis, Charles Williams, and Mythopoeic Literature: Vol. 21
, Article 28.
Available at: https://dc.swosu.edu/mythlore/vol21/iss2/28