The origins of Elysium lie in ancient Greek mythology.

Elysium, or the Elysian fields, is that part of the underworld that is the final resting place of the virtuous. The highest level of the underworld, Elysium is a land of ease and plenty that is synonymous with paradise. Also known as the islands of the blessed, here is where those who have lived a good life achieve immortality.

If interested, you can find some more information here.