Jan 8, 12:42am
As you are no doubt aware, the term “one way borrowing” comes from John Rateliff, who has done by far the most extensive analysis of the relationship between the writing of The Hobbit and the Silmarillion tradition as it existed at that time. In his discussion about the Elvenking, he writes:
"Given the fluid nature of the unpublished myths, where Tolkien was willing to play around with concepts and occasionally contemplate major changes in the legends, we should ask the obvious question: is the elvenking Bilbo meets Thingol himself or an entirely new character closely modelled upon him – an analogue, as it were? The answer seems to be both: just as the status of The Hobbit itself hovered in Tolkien’s mind between being part of the legendarium and standing apart from it, so too within the book the identification of the elvenking straddles both options and cannot conclusively be resolved either way. Even after Tolkien eventually, towards the end of the work on The Lord of the Rings, committed to the decision that the wood-elf king was a separate character, he never fully reworked the original story to completely support that decision.”
In the course of his analysis, John notes that the Elvenking in The Hobbit is far more consistent in character with the original figure of Tinwelint (Thingol’s predecessor in the earlier versions of the legendarium), than the more ennobled Thingol himself. He concludes, “In the end it seems clear that when he wrote The Hobbit Tolkien drew on the old story (which was, after all, unpublished and likely to remain so), changing it as he did so, to make the material more suited to his new purpose. But he left his options open as to whether the Elvenking was a new character or an old familiar character appearing in a new story, slightly altered to fit his new surroundings. In time he decided that the Elvenking was indeed a new character and gave him a new name and history of his own, but this decision postdated the publication of The Hobbit, probably by more than a decade, and he never went back and re-wrote the key passage in The Hobbit to distinguish what was now the analogue from the original. Thus to this day we are left with two contradictory accounts of which elvenking was responsible for provoking the elf-dwarf war, the one in the Silmarillion tradition, and the other within The Hobbit.”
Then, in addressing the thorny question of whether the Arkenstone could have actually been one of the Silmarils, John reminds us that while decades after the posthumous publication of The Silmarilion “it seems inevitable that the three jewels would be lost beyond recovery” at the time that he was writing The Hobbit, “Tolkien had in fact at that point changed his mind four times in the previous fifteen years about the holy jewels’ fate, all in a series of unpublished works that remained in flux and were each to be replaced by a new version of the story; the one constant had been that the story ended with all three of the jewels remote and inaccessible. Just as the sword of Turgon King of Gondolin had somehow survived the fall of his city and found its way through the ages into that troll-lair and hence Bladorthin/Gandalf’s hands, it is thus more than possible that Tolkien was playing in The Hobbit with the idea of having one of F¸anor’s wondrous Jewels re-appear, no doubt the one that had been thrown into a fiery chasm and lost deep within the earth – which is, after all, exactly where the dwarves find the Arkenstone, buried at the roots of an extinct volcano. As with his borrowing regarding Tinwelint’s quarrel with the dwarves in “The Nauglafring" for the chapter about the wood-elves and their king’s old quarrel with the dwarves, Tolkien drew on his legendarium without committing himself: it was a one way borrowing in which elements from the 1930 Quenta and Early Annals found their way into The Hobbit but that ‘unofficial’ usage did not in turn force changes in what Tolkien was still thinking of as the main line of the legendarium.”
To this I have little to add, other than to say that if you have not read John’s cogent and extensive analysis, please pick up a copy of his History of The Hobbit. It is well worth the time.
'But very bright were the stars upon the margin of the world, when at times the clouds about the West were drawn aside.'
The Hall of Fire