Like many, I have just read The Hobbit again, which I hadn’t done since reading it to Veronica as a girl. Even when solemn, Tolkien knows what he is doing with language. It was at his most relaxed that he could be careless, as in the early pages where he too often repeats dreadful (in its modern sense). But he does not employ the ‘Wardour Street’ fake antique that Fowler complained of in others: words like anent, trow, ween, whilom or wot. As a professional philologist he knew the history of every word he used.
Some of the words that give a feeling of antiquity to The Hobbit end with –en. This suffix is used in six different ways in English, and I won’t go through them all. Tolkien uses one kind twice in a single line of the song sung while the barrels are being rolled from the cellars of the Elvenking. ‘Back to pasture, back to mead, / Where the kine and oxen feed.’ Ox is the only word in general use that retains the original Old English plural ending –en of the weak declension. You may ask: what about children? In Old English the plural was cild (pronounced child). In the high Middle Ages the usual plural was childer (as Herod slew in the carol). In the south of England especially, this was newly reinforced with the –en termination of other old plurals, hence children. As for kine, as a plural of cow, it replaced the earlier cy (which some people in Scotland are still supposed to use, though I’ve never heard any doing so). Cows was hardly known before the 17th century, and in Joseph’s biblical dream analysis we still have the seven fat kine.
In The Hobbit Thorin Oakenshield’s name has the proper adjectival form of oak. Some such forms we retain naturally (woollen, wooden), some have become archaic (earthen, wheaten). In the south-west they are meant to say glassen and papern. Do they?
As for elven, as a variant of elvish, it was used in the 14th-century Guy of Warwick and revived by Tolkien, as the OED now records. But on its first use in The Fellowship of the Ring his publishers misspelt Elvenking as Elvinking.