Plenilune, a desuetude word... or not?

Plenilune: The full moon or the time of a full moon.

Michael Quinion, in his latest "World Wide Words" newsletter says that the word "plenilune" has fallen into desuetude.

"...

In a letter to his aunt in 1961, J R R Tolkien wrote of this word that it was beautiful even before it was understood, that he wished he could have the pleasure of meeting it for the first time again, and that "Surely the first meeting should be in a living context, and not in a dictionary."

Tolkien employed it in The Adventures of Tom Bombadil, published in 1962:

[Habergeon: A sleeveless coat or jacket of mail or scale armour.]

A rare recent sighting is in William Weaver's translation of Umberto Eco's Island of the Day Before (1995): "You can see ... when recur the Sundays and the Epacts, and the Solar Circle, and the Moveable and Paschal Feasts, and novilunes and plenilunes, quadratures of the sun and moon."

..."

The Italian word for "plenilune" is plenilunio. I have most beautiful memories of plenilunes, and I hope this word will never disappear from our dictionaries.

By the way, I also like very much the word desuetude. In Italian we have quite a few parole desuete which enchant and enrich the reader's heart and ear.