And the other planes, like Phyrexia (basically "land of Phyresis") seem to have etymologies for their names...
So, what's the etymology of the name Eldraine?
While searching for a etymology for Eldraine, I could not find anything. However, according to the official Magic the Gathering website, as well as what the card say, we do know it is a fusion of multiple fairy tales.
This is speculation without WotC citation, but my guess would be:
First part coming from eldritch, it's own etymology described here.
Less certain about the second part (maybe it just sounded good), but in both English and French the suffix -aine means "approximately".