There's 10 pre-defined names for each civ, for both ages and genders. Forty total = 10 Male Ancient, 10 Female Ancient, 10 Modern Male, 10 Modern Female. I just had a look at a couple of civs on the wiki site and they seem to all be present... are you able to cite which civ and name prompted this topic? It would be interesting to try and track down where the name has come from.
It makes me wonder if there's some clever script in there with dual-civ leaders that allows them to choose from the name pools of both civs they can represent.
As far as renaming citizens, I just edited the xml file for Australia becasue I enjoy random silliness like that - citizen names, city names, geographic feature names.