Well the Rhino Grille came from
Daktari, an old kids tv show.
The rest I'm not too sure on, they have been explained over on IFSJA many times I'm sure. I would figure the name for the Razor comes from the fact it looks like the guard of an old electric razor.
The Cheese Grater one obviously comes from the kitchen utensil because it has that look to it.
The Egg Crate/Boobie is along the same lines as the grater, named for what it resembles, either going off the grille or the orange lights within the grille.
The Pig Nose is named as such because it is the only one that instead of being mostly flat-ish and peaking in the middle, it runs flat where the lights/pie plate holes are and then begins to stick out two inches or so more where the radiator is.
The Final Type is clearly named because it is the final grille made for these vehicles.
The only one I'm not as sure about is the Muscle Grille, since to me its rather weak since it is made of plastic.