The Tennis Court Oath was a pledge that was signed in the early days of the French Revolution and was an important revolutionary act that displayed the belief that political authority came from the nation's people and not from the monarchy.
Why the Peculiar Name?
The pledge thanks its name to the place where it was signed. On June 20, 1789, the Third Estate, representing the commoners in the Estates General, found themselves locked out of their regular meeting place and saw it as a ploy from the King to disband them. The 576 members moved their meeting to a tennis court in Saint-Louis, Versailles and signed an oath that they would not stop meeting up until they have written a new constitution for France. As the Third Estate didn't have the right to act as a National Assembly, this pledge is seen as a revolutionary act.