Ghosts, as everyone knows, are invisible, unseen.
So it is with the ghost writer; he is the unseen anonymous person who actually writes for hire or love the articles or the speeches that a prominent person gets the credit for having written.
Until a decade or so ago such persons, from about 1850, were just called ghosts, somebody thought it a bit more dignified to add “writer.”
In fact, ghostwriting is an honorable profession these days. Recent presidents, engrossed upon important affairs of state, have had no time to prepare public speeches that are, say, primarily political in nature.
Someone who is familiar with the views of the important person is called upon to write the speech that will be used, but the public is led to believe that the important personage has himself written the speech.
Ghost writing has become such a profession these days that ghosts may be found who, for a price, will write a speech, an essay, or an article upon any given subject.
Even an occasional book, ascribed to some “big shot,” is actually the work of a ghost.