I can't imagine this hasn't been discussed earlier, but I never saw it. So:

 

What does "birth" mean in that prophecy everyone knows by heart? Does it have anything to do with the theories of Elayne giving birth to her children, or is it something completely else?

twice dawns the day when his blood is shed,

once for mourning, once for birth

 

just replace "his" with aiel and you get

 

twice dawns the day when aiel blood is shed,

once for mourning, once for birth.

 

Their blood was shed to allow him to be born on dragonmount, and their blood will be shed at shayol ghul for his death.

That's a good theory. And, IIRC, this one was why he (and many readers) thought he would die (with or without being resurrected).

or the Prophesies had a spelling error and its "once for morning".

It is translated multiple times, and ALL Aes Sedai speak the OT. Do you think no one ever mentioned the word they read in the OT didn't mean "mourning", but "morning"? Come on.

there might be interpretation issues but there wont be any error in the translation

I'm pretty sure that was a joke.

 

You wetlanders and your sense of humor...

 

 

And here's how it went down. When you give a prophecy, you just space out and speak. Somebody else has to record it. When the one giving the prophecy said "Once for Morning, Once for Earth" the lady writing it down totally misheard and wrote down the wrong thing.

or the Prophesies had a spelling error and its "once for morning".

 

No. The Prophecies are in the Old Tongue. There's no reason to assume that morning and mourning are phonetically similar in the Old Tongue.