You've uncanned a worm or two ...
The Latin for heaven is: caelum. And the Romans would have pronounced it KY loom. But, first of all pronunciations change over time, so the languages like French and Spanish which are descended from Latin no longer use the original sound system - they've developed their own. The Catholic church has been using Latin itself for quite a while, and has developed its own version of Latin noises as well. You might well find them pronouncing it something like . Secondly, Latin is an inflected language, which means that information which we get in English from the position of a word (noun or adjective) in the sentence is given in Latin by the ending of the word itself - like ; we know it's not the same as . But in Latin it could be amat or or , all with the same meaning.
Regina caeli is
Queen (
Regina) of heaven (caeli) - there the -i ending tells us that it's the genitive or possessive case, ie it gets the word in front when we translate it. And in the Pater noster, actually means - caelis is a plural for some reason.
Needless to say, the fact that caeli can sound like
Kylie is where the resemblance ends! Here endeth the first lesson - hope you find it useful ...