This breed has several names- the most common are Myotonic, Tennessee Fainting, Nervous, and Scare goats. The names refer specifically to myotonia congenita, a condition in which the muscle cells experience prolonged contraction when the goat is startled. The transitory stiffness associated with these contractions can cause the goat to stop moving, stiffen, and even fall down. This is not a true faint, but a muscular phenomenon unrelated to the nervous system. The actual degree of stiffness may vary widely from goat to goat and is based on a number of factors, including age, species purity, and degree of fright.
As strange as this may sound, these little critters have actually served an historical purpose. Shepherds often kept the goats in with their flocks as insurance in case of predator attacks. The theory went something like this- as wolves would come down from the hills to attack a flock of sheep, the goats would become startled and, as per the name of their breed, they would faint. The sheep would make a clean getaway, as the wolves would focus on the stunned goats rather than pursue the fleeing sheep. Not that wonderful if you were one of the goats, sure, but downright dandy if you happened to be a sheep.