A quick search on google gave me this link
(page 28),which states and almost confirms your theory. I say almost because it seems it's also a theory of the author of the essay. I must say, I didn't remember that name from the Kalevala (it's been some years already from the last time I grabbed that book).
It's really not a surprise the enciclopedic knowlegde of Tolkien behind his work. The lecture of the word in discussion seems to have several layers in deepness. Just to name, the use of the terms "heavenly father" or "all-father" in european and biblical literature and how he manages to use it all at once in an ethymology that he doesn't even bother to reveal to the public.