"The term fourth estate is frequently attributed to the nineteenth
century historian Carlyle, though he himself seems to have attributed it
to Edmund Burke:

Burke said there were Three Estates in Parliament; but, in the
Reporters' Gallery yonder, there sat a Fourth Estate more important than
they all. It is not a figure of speech, or a witty saying; it is a
literal fact, .... Printing, which comes necessarily out of Writing, I
say often, is  equivalent to Democracy: invent Writing, Democracy is
inevitable. ..... Whoever can speak, speaking now to the whole nation,
becomes a power, a branch of government, with  inalienable weight in
law-making, in all acts of authority. It matters not what rank he has,
what revenues or garnitures: the requisite thing is that he have a
tongue which others will listen to; this and nothing more is requisite.

                                                         Carlyle (1905)