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

[Estelyn Telcontar]

I have a couple of additional examples for the use of "thou". In these cases, they are found in the context of poetry/song. Gildor's Elves sing:

Gilthoniel! O Elbereth!
Clear are they eyes and bright thy breath!
Snow-white! Snow-white! We sing to thee...

Later on, we read that the last lines of Galadriel's song translate:

Maybe thou shalt find Valimar.
Maybe even thou shalt find it.

Her poetic messages to Aragorn and Legolas were already mentioned, I think.

Does poetry use the familiar form for some special reason? I do know that in some languages (French, and sometimes English, for example), otherwise silent syllables are pronounced in poetry and song, illustrating the fact that the lyrical use of language can differ from normal conversation.

Or can the use of "thou" in singing to a goddess such as Varda be compared to the familiar use in prayer?