That's not really what I mean... I shall give you an example.
In the Netherlands there are 2 restrictions: 1) you can't give a name people can make jokes of 2) you can't give a name which is only used as a last name. For instance Jansen is a very common last name, but not in use as a first name. But Thomas is both used as a first name and a last name. So that's allowed. And Jansen isn't.