Reading this article, the white house reporters are called "The poor slobs of the fourth estate". Not being familiar with this, I equated the media to a fourth branch of government, providing a check and balance on the legislature, the executive, and judicial branch, but I would think the media would be called the fourth branch if that were the case. Where does this term come from, and what is it's meaning?
In France, prior to the Revolution of 1789, there were three estates of the realm. These were the clergy, the nobility and the common people. The king belonged to none of these. Similar divisions of society existed across Europe. The Estates General was a kind of parliament in which all three of the estates were represented, although in practice the common people were represented only by the bourgeoisie or prominent townspeople. The word estate is similar to the word state in the sense of a state of life.
In the UK today the clergy and nobility are represented in Parliament by the bishops and lords in the House of Lords, while the common people are represented in the House of Commons.
In the early nineteenth century with the growth of newspapers and the increasing influence of journalists they began to be called the "fourth estate", a perhaps somewhat cynical recognition that a successful government not only had to satisfy the interests of the church, the nobility and the common people, but also had to take account of the views of the press.
So it is not a reference to the press as a fourth arm of government, along with executive, legislature and judiciary. Rather it is a fourth section of the population along with the church, the nobility (equating to the rich and powerful) and the ordinary people.