How did fool birds aka ruffed grouse get its name?

The ruffed grouse (Bonasa umbellus), also known as a foolbird, gets its name from its unusual behavior when confronted by a predator. When threatened, the grouse will typically remain motionless, often fluffing up its feathers and holding its wings slightly spread. This behavior, along with its prominent eyes and overall color pattern, is thought to make the grouse appear larger and more threatening to potential predators, confusing or fooling them momentarily.