I hadn't realized the combination of those three names, Zenaida Fernandez Gonzalez, was that common though.
Fernandez
Hernandez
Perez
Martinez
Gonzalez
the list goes on an on. I'm no expert, but I think I recall it's a combo of the mother's and father's surnames, yes?
And I believe the "undocumented" angle factored into Casey's knowing how difficult it would be to find ZG if GM and/or GP went looking if/when they threatened to take Caylee away (again).
IMHO