Here's why:
* Different Species: Gerbils and chinchillas are different species, belonging to different families. They are too genetically distinct to produce viable offspring.
* Hybrids: While hybrids between closely related species exist (like a liger, a lion-tiger mix), gerbils and chinchillas are too far apart on the evolutionary tree for such a hybrid to occur naturally.
So, there isn't a special name for a gerbil-chinchilla mix because it doesn't exist.