Thanks a lot for doing that research. For the bit of research I've been doing, it does look like caelum is the original root of celestial, and 'cae' seems to be where the word sky originates from. In Latin it seems to most often refer to the sky or to heaven, but also has a second meaning that refers to a sculptor's chisel, which is supposedly the main inspiration for naming the constellation this, I guess it looks like a chisel.
Some cool quotes I found with caelum in them:
"fiat justitia ruat caelum translates to “may justice be done though the heavens fall.”
caelum certe patet means "the sky at least stands open"
Awesome depth of meaning.
Think I'm gonna pronounce it KYE-lum too, cuz for one, that's actually the way it's pronounced in the original Latin (though there does seem to be some debate about this). Could add an L (Caellum) and it actually would become a Celtic name meaning 'brave warrior' that would originally be pronounced KAY-lum, but I think I'll just keep that as a loosely connected kinda meaning.
And for another, he'll be a 1/2 Chinese kid, and we can easily use the KYE sound when coming up with a good Chinese name, but there aren't any KAY sounds in Chinese (we'd really like both his names to have a similar pronunciation, and have an equally awesome Chinese meaning (we live in China, and he'll probably be raised here)--- his Chinese name will probably be Kai-Long-- don't know for sure yet though, that'll require us a bit more research--- but in any event KYE-lum will be much easier to get close-ish to in Chinese than KAY-lum would).
And thirdly, I really like the nickname Kai (Cae). Has meanings in tons of languages itself. A good stand-alone name even on it's own.
And yeah, I feel like KYE-lum sounds a bit more masculine (like Kyle or Rylan) than KAY-lum does.
And even if it is mispronounced sometimes, even the mispronunciations will usually sound nice--- probably would usually be mispronounced as either KAY-lum or Callum.
I'm just liking this name more and more the more I learn about it and think about it.