"Lupin" and "Lupine" are alternate renderings of the name of the same genus, "Lupinus". The "us" is a Latin nominative ending un-needed in English, so it was dropped, but there were two different ideas regarding what to do with the ending of the word.
"Lupine" is the English word corresponding to the Latin word "lupinus" meaning "wolf-like". Why are Lupines "wolf-like"? Well, a long time ago it was noticed that they tend to live on barren lands, and it was assumed that they were ravenously sucking all the fertility out of the ground.
One of those cases of getting cause and effect backwards: Lupines live on naturally infertile land, because there they have the advantage over competitors, harboring, as they do, nitrogen-fixing bacteria in their roots.
Some people call them "loco weeds", because the poisonous alkaloids in their tissues will make grazing animals behave oddly.
You expressed some interest in the New World cultivated edible Lupine, Future, from the Andes. In the Old World, 3 species were cultivated for food, and like the Incas, the peoples of southern Europe and the Middle East leach out the poisons.
But in the 1920s, German breeders experimented with breeding the toxins out of the Lupines. I dunno if the whole plant is poison-free, or just the seeds (which is the only part humans are interested in). It would be ideal if the plant were toxic (to deter predators) while the seed were edible to humans.
They stopped growing them in Germany, apparently, perhaps due to cost issues, but they are now grown in France and especially in Australia. In Australia a fairly major crop.
They are ground into flour with which to enrich wheat flour for making pastries and breads. It significantly improves the amino acid balance, plus it adds some white soluble fiber that does not seem to impact the flour much. The protein content is not as high as soybeans, but it is higher than that of most other Legumes other than soy and winged beans. The carbohydrate content is lower than with other pulses. And they grow in much cooler (and potentially slightly drier) climates than soybeans can tolerate. They can be planted in the Autumn in Mediterranean climates, live over the winter as a cover crop to protect the soil and take advantage of the winter rains, bloom in the spring, and be harvested in the summer.
One problem worth mentioning: anyone allergic to peanuts is allergic to Lupine. About 2% of the population of Europe will keel over in anaphalactic shock if fed pastries with Lupine flour in them. It's already happened. And they haven't been printing warning labels on it. I dunno what the percentages are in other parts of the world, but peanut allergies are pretty common and are frequently deadly. I've heard of kids dying from eating a chocolate chip cookie that had a small amount of ground peanut to enhance the flavor. I know a friend of the family is extremely allergic. Always worried about feeding her and forgetting that there were a small amount of peanut in something.
I suppose one other warning: people keep confusing which ones are "sweet" and which are bitter. Plus, people from the Middle East and southern Europe are used to the bitter variety, sometimes grow them, and risk contaminating crops with bitter genes.
As a result, something else that has happened, is that buyers have bought bitter Lupines not realizing that there was a difference, ground them into flour, and given the consumers Lupine poisoning. If Lupine meal or seed is bitter, don't eat it (until and unless the toxins safely leached out).
