There are other names for just about everything in the food world, and in this case, butter beans is the other name for lima beans. There are two common varieties of lima bean - the baby lima bean and the Fordhook - but don't confuse them as the same bean in different stages of development. The Fordhook is larger, lighter in color, and has a stronger taste than the baby lima, but it is not a grown-up baby - it is a separate variety.
In the south of the United States, Fordhook lima beans are commonly called butter beans. Indeed, one of our readers says many southerners wouldn't recognize the name lima bean. These larger beans are also known as butter beans in Europe, or Madagascar beans, since most lima beans sold in Europe are grown in Madagascar (or Mauritius).
They can also be called calico beans, but that may be only when they're speckled with a bit of purple.
We know just enough Canadian to suspect that butter beans are called lima beans most everywhere other than Quebec.