When we first considered the pattern of archaic words, I had decided ahead of time that these would indicate high register. I think I’m going to have to let go of that for now. Our green line of archaic words does indicate a general rise toward the rhetorical climax of the book.

But only 32 words out of 1534 uncommon ones – that’s 2% – qualify as archaic! We simply don’t have robust findings, as the statistician part of my mind would say.
Let’s set aside the drive to prove something and have a look around. We discussed earlier that archaic words signal elves in nearby scenes – a reminder that elves live much longer than hobbits. Elves speaking the same tongue as Bilbo will have learned it centuries before he did and have a lovely old-fashioned diction in that hobbit’s opinion. As we noted, however, it is the word “merry” which fills most of this trend. Do thousands of years of life contribute to merriment? Let us hope so.
When archaic words drop to nothing at all, those are goblin scenes. Alert Word Fan Grace commented that “elf” and “goblin” may have been interchangeable words in literature before The Hobbit and that Tolkien probably tapped different parts of his vocabulary to express the huge contrast between the different peoples about whom he was writing. Google’s Ngram viewer indicates through most of the nineteenth century that the two words were used at about the same rate, a suggestion that the words could have been used interchangeably, but before that the Norse-derived word “elf” had been strongly preferred in written English to the French-derived word “goblin”.
We also noted that the goblin scenes are bereft of food words as well – and that when food words are low, Tookishness trends upward! It’s probably all to the good that Bilbo’s adventurous spirit rises when there are goblins about, now that I think of it.
Tolkien used a light touch with archaic words. Compare his density of old forms with that of a writer who influenced him, William Morris who piles on real or invented strong past participles, thees and thous, kennings, and poetry in his work House of the Wolfings. Tolkien enjoyed that story and then improved on the archaic techniques. He never slowed us readers down by making us puzzle out his meaning.
I still have a drive to chase down archaic words, turns of phrase, and syntax; perhaps in The Lord of the Rings next. I do admit that I spotted dozens of places in The Hobbit where I expected to see a subjunctive form and didn’t. It’s a good thing the road goes ever on!
Morris, William. The House of the Wolfings. Project Gutenberg. Kindle Edition.