What’s Up With the Title?
The easiest answer to this question is that Orlando: A Biography is about Orlando, hence the title. But this book seems to be self-conscious about its status as a fictional work: "the biographer" is constantly inserting ironic remarks about the difficulty of writing about Orlando's long and uneventful life. Most authors name their biographies after their subjects because their subject (i.e., Miley Cyrus) comes before the book (i.e. Life of Miley: An Unauthorized Biography). In the case of Orlando, the reflexive, jokey tone of the novel highlights that Orlando the person is coming after the novel. The novel is producing Orlando the person; the main character of the novel and the novel itself are basically the same thing.
Something else that's interesting about the name Orlando is that it's a name with a strong literary pedigree. Orlando is one of the heroes of Shakespeare's As You Like It, and is also the name of Italian Renaissance writer Ariosto's Crusading hero in Orlando Furioso. Shakespeare's Orlando, like our Orlando, is a poet – and Shakespeare's Orlando, like our Orlando, falls in love with a person of ambiguous gender. In As You Like It, Orlando falls in love with Rosalind, who disguises herself as a boy for much of the play.
Shakespeare loves this trick (check out Shmoop's guide to Twelfth Night) and so does Virginia Woolf. (Think of Sasha's initial appearance to Orlando as a boy, the cross-dressing Archduchess/Archduke, and, of course, Shel, who's as androgynous as Orlando.) Woolf' use of this otherwise unusual name to connect Orlando to other literary heroes that have come before her, suggests that Orlando is not only a written character, but also a character who is about writing.