A Elbereth Gilthoniel

From Tolkien Gateway

A Elbereth Gilthoniel is an aerlinn (poem) of Rivendell addressed to Varda, sung in Sindarin and in iambic tetrameter. The first stanza (the only one known) rhymes aababcc.

A Elbereth Gilthoniel
Silivren penna míriel
o menel aglar elenath!
Na-chaered palan-díriel
o galadhremmin Ennorath,
Fanuilos, le linnathon
nef aear, si nef Aearon.

Which translates as

O Elbereth Starkindler
(white) glittering slants down
sparkling like jewels
from [the] firmament [the] glory [of] the star-host!
To-remote distance far-having gazed
from [the] tree-tangled middle-lands,
Fanuilos, to thee I will chant
on this side of ocean, here on this side of the Great Ocean!

The rest of it is not saved but it is possible that 'Oh Snow-white' is a Westron translation or variation of this aerlinn. Variations of this hymn are sung throughout the book, such as the very last one written down:

[ Frodo Baggins has just sung a song]

..And as if in answer, from down below, coming up the road out of the valley, voices sang:

A! Elbereth Gilthoniel!
silivren penna míriel
o menel aglar elenath,
Gilthoniel, A! Elbereth!
We still remember, we who dwell
In this far land beneath the trees
The starlight on the Western Seas