Etymology

The three 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 (though they changed over time). 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.

Noun

1. A hypothetical fourth class of civic subjects, or fourth body (in Britain, after the Crown, and the two Houses of Parliament) which governed legislation.
   • 1603, John Florio, translating Michel de Montaigne, Folio Society 2006, vol. 1 p. 104:

     What is more barbarous than to see a nation [...] where justice is lawfully denied him, that hath not wherewithall to pay for it; and that this merchandize hath so great credit, that in a politicall government there should be set up a fourth estate [tr. quatriesme estat] of Lawyers, breathsellers and pettifoggers [...].

2. Journalism or journalists considered as a group; the Press.