From The Food Encyclopedia by Jacques Rolland and Carol Sherman
Also snap bean, string bean. A long, thin green pod containing seeds; both the pod and seeds are edible. At one time a tough thin string ran down the center of the bean that had to be removed before eating, thus the name "string bean." Today, most green beans available in the market are stringless. The "snap" refers to the sound the fresh beans make when broken in two. See also asparagus bean, bean, haricot bean, haricot vert, runner bean.
