Glenn traces the origin of The Secret History in titles, and notes that secret histories are a dime a dozen. That's true
The only thing he missed is that naturally, once a Secret History is published, it's no longer a secret. Should the titles of subsequent editions be changed? The Secret History of Mosdow then becomes The History of Moscow ... but those four words standing alone just don't have the same ring. Descriptive, yes, but alluring, no. Still, "secret" has been used often enough to blunt its effect. So writers and editors will have to come up with another adjective soon. I think "Confidential" is starting to lose its attention-getting power (I had one titled PC Confidential back in 2000). Ditto "hidden," and definitely "... don't want you to know."
Especially "... don't want you to know." Like, "the selling secrets eBay doesn't want you to know?" (A line used by a spammer.) Right--eBay really doesn't want its sellers to sell more for higher prices. Not a chance!