Ishgard variants for Elezen and Hyur

[Berethos]

Yep.
It works like this:
During the First Astral Era, Elezen were the first to inhabit Eorzea, living in its vast plains. Hyurs came and started to take over, so the Elezen left, some going north to Coerthas, forming Ishgard, and some going to the Shroud, forming Gelmora. From the Gelmora Elezen, some of them went underground, becoming the Duskwights, while those who stayed on the surface would eventually form Gridania with the Hyurs.

Except for the Astral Era part, this is essentially correct - the above happened early in the Sixth Astral Era (which lasted nearly 1600 years).