Zaydi al Qahtani was the leader of the Geziri tribe who got too close to the humans (more than all other Daeva tribes) and adopted their name for the Daeva - "Djinn". He, together with the other tribes, invaded Daevabad, where the Nahids were overseeing and ruling the Daeva world. The Qahtanis are still ruling the city of Daevabad to this very day; this was ~1400 years ago.