Good comments guys. I agree.
I have had one friend make it quite plain, all they expect to do, is show up, make a ultra plain fighter, because they have no particular interest in taking the game any more seriously than a talk show on TV.
If they show up next game session, it's more by accident than intent.
That's really just a contempt for the fact, that a good game doesn't pop out of thin air, the guy hosting it had to actually DO something to make it happen.
It's not like the DM just made his game appear as easily as turning on a tv station and presto show appears.
A dumb name is likely an indication the person's interest is as you say, very marginal. Far better to confront the person, and put them on the spot "are you seriously interested in the game, or are you just holding down the chair with your butt for a few hours?". I'd rather have the person just as a guest that can watch the game if they are cool with that. They can be the one to freshen up drinks if they need a sense of being useful.
In my case, it was a girl, and she was really only there for the socialising. Didn't really give a hoot about the game.