A concussion is a violent blow, especially to the head, that often injures the brain or causes a loss of consciousness — an all-too-frequent occurrence, unfortunately, in contact sports like football or boxing.
First used around 1400, concussion originates from the Latin concussionem, which means "a shaking." Your brain certainly gets "a shaking" when you take a heavy blow to the head, which sometimes causes injury or permanent damage. It's not just people, though, who get concussions; a building can also suffer from a concussion during an earthquake.
