Both butter beans and lima beans come from the same species of plant, Phaseolus lunatus. The difference lies in their maturity.
Lima vs. Butter, What's the Diff
Butter beans and lima beans come from the same species of bean plant. The name “butter bean” typically refers to the mature, pale, cream‑colored stage, while “lima bean” often refers to the younger, greener stage. The two stages of beans are identical in nutrition, and like most beans are excellent sources of protein and fiber. The more mature butter beans hold up better to extended cooking and are described as having a creamy texture, which may be the origin of the name butter. Butter beans are sometimes sold as "large limas." Lima beans, the young ones, tend to be firmer and less starchy and are suited for quicker cooking. They may be sold as young or green limas.
Why the Name "Lima Bean?"
The beans are native to South America, particularly the region that is now Peru, and they were cultivated for thousands of years before the Europeans arrived. Ther colonists continued cultivation and beans for export were usually shipped through the port of Lima, Peru and the shipping bags were marked with the port of origin - Lima, Peru. The name stuck and hence they are now known as Lima beans. It has occasionally been suggested that the name derives from the color resemblance between the young, green beans and the citrus fruit lime, but the Lima, Peru origin for the name has a lot more credence.
This bean has a fairly long list of less commonly used nicknames, in the American South and elsewhere, including sieva beans, Madagascar beans, and chad beans.
