Eowyn…

I’ve been re reading Lord of the Rings now that all the movies have been and gone, and the books weren’t going to ruin my enjoyment of them.
It’s probably been 15 years since I last read them – I did make an attempt about 7 or 8 years ago, but for some reason I didn’t like the writing style the second time around, and gave up.
However, this time I have no problem with it, and am enjoying the books quite well – even the Frodo and Sam bits.
But there’s one little thing that’s kind of bugging me –

Why the hell does Eowyn revert to Thees and Thous whenever she gets emotional?
No one else in the books talks like that..not even the elves or the men of Gondor (and they be pretty uptight at times), and even she doesn’t do it most of the time, only when she’s not getting her way.
I would have thought that if your speech was going to change when you got upset, it would be to revert to something more simple, rather than some pretentious formal idiom that no one else uses.