This is a very interesting topic. And, of course, I'd like to introduce the Finnish point of view.
While exploring the Sindarin and Quenya vocabulary you find delightingly many words that have to do with Finnish. Sindarin
gannel for 'harp' is very similar to
kannel (the Finnish national instrument which is related to the harp). Also
tië for 'path' is almost the same as Finnish
tie 'road'. I've also wondered if the stem
lin- 'sing' has to do with the Finnish word
lintu 'bird', but that might be a bit far-fetched.
It is also very interesting that in Quenya
-atar is a masculine ending since it means 'father', but in Finnish the ending
-tar (or
-tär) is feminine, eg.
kuningas (king) ->
kuningatar (queen),
tarjoilija (waiter) ->
tarjoilijatar (waitress) and so on... No wonder I thought Ilúvatar to be female while first seeing his name...