I came across the word "lemmings", being used in the following context, "...followed like so many lemmings into a sea of western delusions." I vaguely know that a "lemming" is an animal (rodent?), but what is the story behind it? One dictionary described them as being in large groups and that they are often, but wrongly, thought to jump off cliffs together (Cambridge Dictionary). Yet, AHD says, that they are "Any of various small, thickset rodents, especially of the genus Lemmus, inhabiting northern regions and known for periodic mass migrations that sometimes end in drowning."
Do they jump off cliffs or migrate and end in drowning--or neither? Does anyone know the story behind them?