Dear pamb:(taken fron the Internet)

Its coinage, with its present meaning, has been attributed to Edmund Burke
(1729 - 1797), a British politician. It comes from a quote in Thomas Carlyle's
book, "Heros and Hero Worship in History" (1841).

"Burke said that there were three Estates in Parliament, but in the
Reporters Gallery yonder, there sat a fourth Estate more important far
than they all."

The three estates in the above quote refer to the British parliament, the
Lords Temporal, the Lords Spiritual and the Commons. The Lords Temporal
and the Lords Spiritual combined being The House of Lords, the upper House
of parliament. And the Commons is The House of Commons or the British
lower House.