How I Stopped Worrying and Learned to Love Eberron
Like many mixed races, the half-elves are a unlikely mix of genetics and magic. Elves, though native to Xen’drik and known mostly in Aerenal, have always had a presence on Khorvaire. Some Valenar elves stayed behind after their war with the Dhakaani Empire and greeted the human explorers. Elves associated with what would become House Phiarlan left Aerenal after the destruction of the Mark of Death. And there have always been elves outside the mainstream of their culture who simply explored the world and ignored centuries of tradition. All these elves soon met humans, and the differences gave way to any number of factors and half-elves were born.
Since the half-elf race originated in Khorvaire, and they are almost never found elsewhere naturally, so they took to calling themselves after their homeland; the Khorvar. They have also become an integral part of Khorvaire society through their two dragonmarked houses, House Lyrander and House Medani.