Part of me thinks it's about having so much power over a man that one could strip away his masculinity and feminize him. Those of you with an appreciation for the past might want to look further into the story of Sporus. He was a Roman boy who was castrated and taken as a wife by Emperor Nero. When Nero died, Sporus was passed around the the most powerful men in Rome all the while effectively being treated as a woman.
https://en.wikipedia.org/wiki/Sporus