fourth estate

Etymology:

• The three estates were originally the three classes of people who could participate in government, either directly or by electing representatives – originally the clergy, barons/knights, and the commons. Later the "three estates" were misunderstood as being the three governmental powers necessary for legislation: the Crown, the House of Lords, and the House of Commons; from there, the idea of a "fourth estate" was often used in satirical or jocular expressions, before developing a fixed association with the Press.