(Yaisa didn't follow that but probably someone was taking notes and the anxious genius types will puzzle over it later, whatever.)
A slave is... a person who is wholly the possession of another, if you're really hardcore about it regarded by Civilization itself as their property as much as their shoes are. Yaisa is not herself that hardcore; lots of people use it just for aesthetically reminiscent relationshjps that didn't involve paying Civilization to go along with this. When you call someone 'slave' in bed you're not necessarily bringing in the whole thing, just the thing that's hot about it. Probably Keltham is now going to have a million questions Yaisa can't answer because her exposure to this concept is all from disrecommended romance novels titled 'slave of a barbarian' and so on.