Goldberry is "
the River Daughter". She reminds me of a Greek nymph; I think of her as a
Maia of
Ulmo (much as
Melian was a Maia, too). I don't think any
Elf would be called the River Daughter, and an Elf would have relatives, which would not include a River
.
Goldberry, in my mind, is "easy" to figure out.
Bombadil is another matter. I don't think he is
Eru, mostly because Eru is not a buffoon
. It could be said that he is "a spirit", someone who entered
Arda at the beginning, before all other
Ainur (including the
Valar). He would then be another Ainu. Remember that the
Maiar are "the people of the Valar"; so that an Ainu who is not of "the people of the Valar" is not a Maia.
My personal opinion is that
Tolkien just added Bombadil to the story as a "private joke". He had an important plot function, true, but Goldberry could just as well perform the same role; all Tolkien needed was a friendly Maia there.
He was having a joke with his readers (us
).
But if you want to know the REAL truth about
Tom Bombadil, check
this thread.