The "Kunlun slave" in The Longest Day in Chang 'an, did "Kunlun" originate in the Tang Dynasty?

In the history of the Tang Dynasty, Kunlun slaves were indeed a particularly important and novel thing. In fact, in today's words, Kunlun slaves are African blacks. At that time, walking on the streets of the Tang Dynasty, you could often see many black people walking around. Everyone knows that the Tang Dynasty was particularly open and accepted people from neighboring countries, but it is estimated that many people did not expect that blacks appeared in the Tang Dynasty. In fact, people called them Kunlun slaves not because they lived in Kunlun Mountain, but because people in Southeast Asia and South Asia were a little darker than the locals in the Tang Dynasty. Of course, when they saw these black people, everyone thought they must have come from these places. But in fact, these black people are all from Africa today.