Nefermandias
Hero
That's a really cool piece of trivia. Thank you.The term "Githyanki" as an alien race that otherwise have nothing to do with the D&D race was first used in a GRRM novel, Dying of the Light.
Charlie Stross, at the time a teenaged D&D fan but who would later go on to be a sci-fi novelist of his own renown (primarily the Laundry Files novels), took the name but little else when he submitted the Githyanki as monsters to the Fiend Folio. Stross is also responsible for the Slaad and a few other monsters IIRC.