Here's the history of that phrase: It started back in the 70s with his marriage to Ivana; it's a European thing. She called him that when speaking about him to news interviewers, and the media picked it up without really understanding it as a cultural difference and ran with it almost mockingly. I don't speak Czech, her native language, but I know that in Italian this is a polite way to refer to a person with whom you are familiar, but the person you are talking about them to is not (or should not be) on a first-name basis with them.
Oh, I see. That’s done in Spanish sometimes, too.