Origin of The Well of Eternity

In the WarCraft universe, the Well of Eternity was the primary font of magical energy for all of Azeroth. During the War of the Ancients,

We later find in the Cataclysm expansion for World of WarCraft that

Given the relationship of the two and the fact that the Well's origins are never mentioned in any of the games (but possibly are in the books), do we know the origin of The Well of Eternity? Or was it always there and the Night Elf civilization just sprung up around it eons ago?

I've checked the WoW wiki and was unable to find a satisfactory answer. I'm hoping that someone more well-versed in the books or comics might have an answer.