“Thee” and “thou” in “The Lord of the Rings”

[Aiwendil]

I'm pretty sure the change was neither arbitrary nor an attempt at modernisation. I don't have the books at hand at the moment, but I'm almost certain that JRRT himself changed his mind once or twice about "thou" vs. "you" in various places in the Narn.

(I believe (though I could be mis-remembering) that he originally wrote "thou" in some places but later began, but didn't finish, systematically changing every "thou" to "you". Presumably, in UT Christopher Tolkien left this as it was whereas in CoH he completed the systematic revision. I could be wrong about the details, though; I'll try to find the source when I get home.)

[Aiwendil]

Hmm, maybe this is what I was thinking of, referring to the dialogue between Hurin and Morgoth:

As the speeches were typed they were set entirely in the second person singular, 'thou wert', 'knowest thou', etc.; but my father went through it changing every 'thou' and 'thee' to 'you', and the equivalent verb-forms – and changing 'Knowest thou' to 'Do you know' rather than 'Know you' (also 'puissant' to 'mighty'). In this form, of course, the text was printed in Unfinished Tales.

The dialogues with Glaurung and Gurthang originate from a different text (NE, as Christopher calls it), so perhaps they were changed in the interest of stylistic consistency.

I could have sworn I read something else about "thou" and "you" in the Narn, but if so I can't find it.