Nearly everything about the publication of “The Cuckoo’s Calling,” a detective novel released by Little, Brown & Company in April, has been a little mysterious.

Its real author, it was revealed last week, was not Robert Galbraith, as the publisher originally claimed, but J. K. Rowling. That disclosure only led to a flurry of questions: Why had Ms. Rowling, whose Harry Potter series made her famous, wealthy and widely admired, written a book under a pseudonym? Who had unmasked her, apparently against her will? And was it, as the cynics muttered, all a clever marketing ploy to juice sales?

Some of those questions, to the relief of Ms. Rowling’s fans, have now been answered.

Ms. Rowling, never a prolific giver of interviews, has elaborated at unusual length in a new post on robert-galbraith.com, a Web site devoted to her pseudonym.

The name she chose, Ms. Rowling explained, is a mash-up of that of one of her heroes, Robert F. Kennedy, and Ella Galbraith, a fantasy name she chose for herself as a girl.