The kidney bean takes its name from its resemblance in shape to the human kidney, an organ that cleanses the blood of wastes. In turn, the kidney takes its own name from something it resembles: an egg. In Middle English, egg was spelt and pronounced ey, which is exactly how it appears at the end of the word kidney; the other part of kidney—the kidn part—likely derives from an Old Norse word that refers to the anatomical location of the kidney: near the belly, which in Old Norse was called the kvithr. A kidney, therefore, is literally a kvithr ey or belly egg. The name kidney bean first appeared in English in the mid sixteenth century, but a hundred years later the same legume also came to be known as the French bean and as the haricot bean. Haricot, in fact, is the French word for beans in general, a word deriving from what the Aztecs called the bean, ayacotl.
The object under discussion is the distinctly kidney-shaped seed of the green or string bean, which takes on a dark red hue and expands in size as it ripens. Typically, it is allowed to dry before being utilized.
This particular legume, classified as a member of the haricot family, originated in the New World and was introduced to Italy by seafarers during the 16th century. Currently, both the red and white variants of the kidney-shaped bean, commonly referred to as “cannellini,” thrive in Italian cuisine. On the other hand, the red kidney bean is extensively distributed throughout the United States and is a prevalent ingredient in Mexican cuisine, known locally as the “frijol rojo” or red bean. Refried beans, a popular Mexican dish, are also made using this legume.