I grew up calling them butter beans, because that's what my mother called them when she fixed them. I didn't pay much attention to packaging in those days, so I don't know what they were "officially" called. (I grew up in St. Louis, MO; my parents grew up in Arkansas and Kentucky.)

I live in Minnesota now, and I rarely eat them any more because my wife doesn't like them, so I'm not quite sure what the labels say.

I just checked the Green Giant web site (a Minnesota-based company), and I see that under "frozen side dishes" they list "baby lima beans" and under "canned vegetables" they list "butter beans." What's up with that? Are we making a class distinction here?

I also checked Birds Eye. I see that one of their brand names, McKenzie's, which seems to be a Southern-oriented brand, lists "baby lima beans," "butter beans," and "speckled butter beans." All of Birds Eye's other brands—Birds Eye, C & W (which apparently stands for "California & Washington"), and Freshlike—mention only "lima beans" or "baby lima beans."

Wikipedia says they are the same species: Phaseolus lunatus.