the lord of the rings - What's so special about the name "Elessar"?

In Fellowship of the Ring, when giving Aragorn his gift, Galadriel says something I thought was unusual (emphasis mine):

'This stone I gave to Celebrían my daughter, and she to hers; and now it comes to you as a token of hope. In this hour take the name that was foretold for you, Elessar, the Elfstone of the house of Elendil!'

^{Fellowship of the Ring Book II Chapter 8: "Farewell to Lórien"}

This suggests some mythological significance to the name "Elessar," which seems unusual; the only other name I can think of with that kind of significance is Durin.

What "foretelling" was behind the name "Elessar"?

Answer

"Elessar", the name

There's an oblique reference in Return of the King that this name was foretold at Aragorn's birth:

[W]ord went through the City: 'The King is come again indeed.' And they named him Elfstone, because of the green stone that he wore, and so the name which it was foretold at his birth that he should bear was chosen for him by his own people.

^{Return of the King Book V Chapter 8: "The Houses of Healing"}

This is, in turn, expanded upon in a brief note written around the same time as Appendix A, reproduced in The Peoples of Middle-earth:

[H]is father gave him the name Aragorn, a name used in the House of the Chieftains. But Ivorwen [Aragorn's maternal grandmother] at his naming stood by, and said 'Kingly Valour' (for so that name is interpreted): 'that he shall have, but I see on his breast a green stone, and from that his true name shall come and his chief renown: for he shall be a healer and a renewer.'

Above this is written: 'and they did not know what she meant, for there was no green stone to be seen by other eyes' (followed by illegible words); and beneath it: 'for the green Elfstone was given to him by Galadriel'.

^{History of Middle-earth XII The Peoples of Middle-earth Foreword}

"Elessar", the stone

The "green gem" referenced by Ivorwen is obvious the stone given to Aragorn by Galadriel, so what of that stone? For that, we turn to Unfinished Tales.

The Elessar was a gem made in Gondolin in the First Age, purported to have healing properties:

[I]t is said that those who looked through this stone saw things that were withered or burned healed again or as they were in the grace of their youth, and that the hands of one who held it brought to all that they touched healing from hurt.

^{Unfinished Tales Part Two: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn"}

It was in the possession of Eärendil when he left over the Sea, and so left Middle-earth. At this point, there are two distinct stories for the second stone; as Tolkien writes:

In ages after there was again an Elessar, and of this two things are said, though which is true only those Wise could say who now are gone.

^{Unfinished Tales Part Two: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn"}

1. 
   
   

   In one version of the story, Gandalf brought the original Elessar with him when he came to Middle-earth in the Second Age, and presented it to Galadriel with the instruction that she eventually pass it on (to Aragorn):

   
   

   
   

   [S]ome say that the second was indeed only the first returned, by the grace of the Valar; and that Olórin (who was known in Middle-earth as Mithrandir) brought it with him out of the West.

   
   

   [...]

   
   

   Olórin said: "This I bring to you from Yavanna. Use it as you may, and for a while you shall make the land of your dwelling the fairest place in Middle-earth. But it is not for you to possess. You shall hand it on when the time comes. For before you grow weary, and at last forsake Mid­dle-earth one shall come who is to receive it, and his name shall be that of the stone: Elessar he shall be called."

   
   

   ^{Unfinished Tales Part Two: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn"}

   
   

   
   


2. 
   

   In the second version, the Elessar possessed by Galadriel was a different stone, made by Celebrimbor as a gift for Galadriel and passed to Celebrían and then Arwen:

   
   
   

   
   

   [Celebrimbor] took thought, and began a long delicate labour, and so for Galadriel he made the great­est of his works (save the Three Rings only). And it is said that more subtle and clear was the green gem that he made than that of Enerdhil, but yet its light had less power. [...] Wielding the Elessar all things grew fair about Galadriel, until the coming of the Shadow to the Forest. But afterwards when Nenya, chief of the Three," was sent to her by Celebrimbor, she needed it (as she thought) no more, and she gave it to Celebrían her daughter, and so it came to Arwen and to Aragorn who was called Elessar.

   
   

   ^{Unfinished Tales Part Two: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn"}

   
   

   
   

As Hammond and Scull note in A Reader's Companion, neither story is wholly satisfying. The first explains the connection Ivorwen foresaw between Aragorn and the Elessar, but is difficult to reconcile with Galadriel's statement (quoted in the question) that she gave the stone to her daughter.

Unfortunately Tolkien wrote no more on the subject, so we have to be content with the ambiguity.

Earlier versions

Interestingly, the gift of the Elfstone predates the character of Aragorn as we know him; in some drafts it was given to Gimli the dwarf. However, in one particularly hilarious draft, it was given to Trotter, the hobbit who eventually morphed into Aragorn, when Tolkien decided that Trotter's real name should be Elfstone and the gift turned into a play on that name:

'Elfstone is your name, Eldamir in the language of your fathers of old, and it is a fair name. I will add this gift of my own to match it.' She put her hand to her throat and unclasped from a fine chain a gem that hung before her breast. It was a stone of clear green set in a band of silver. 'All growing things that you look at through this,' she said, 'you will see as they were in their youth and in their spring. It is a gift that blends joys and sorrow; yet many things that now appear loathly shall seem otherwise to you hereafter.'

^{History of Middle-earth VII The Treason of Isengard Chapter XIV: "Farewell to Lórien" (v)}