Earlier today a colleague posted on Facebook about the entitled/titled distinction, that entitled must only be used in the sense of "having a right to," never in the sense of "bearing the title." I remarked that that was not reliable advice and was asked, quite reasonably, why.
Bryan Garner, in Garner's Modern English Usage, is succinct: "The word entitle has two meanings (1) 'to provide with a right or title to something' ... and 'to give a title to.' ... But sense 2 actually predates sense 1, and both senses are well established."
Merriam-Webster's, Webster's New World, and the Concise Oxford give both senses of entitle, as does American Heritage, which, significantly, presents no usage note on this supposed distinction. There is no mention of a title/entitle distinction in four editions of Fowler's (I looked).
Why, civilians ask, is this even an issue? It is because the Associated Press Stylebook, which has scraped many barnacles off its hull--but there were so many--advises in the entitled entry, "Use it to mean a right to do or have something. Do not use it to mean titled." This advice I followed for many years, until I didn't.
The title/entitle distinction was also upheld by the late John Bremner, who as the admired (and occasionally feared) Oscar S. Stauffer Distinguished Professor of Journalism at the University of Kansas and the author of Words on Words, had considerable influence on U.S. journalism.
The origin of "rules" like this one lies in editors' relentless pursuit of precision in language, which tempts them to invent distinctions. The Blessed Henry Watson Fowler, in a notable example, expressed a suggestion that English would be tidier if that were only used to introduce restrictive dependent clauses, which only to introduce nonrestrictive dependent clauses. The British have persisted in ignoring this pious wish for the past century, but among U.S. editors it has become a Rule with a status on par with Newton's Four Laws of Motion.
My recommendation is that you should have better things to spend time on than title/entitle, but if you must dither over whether a sentence should read "Mark Twain wrote a book titled Huckleberry Finn" or "Mark Twain wrote a book entitled Huckleberry Finn," just make it "Mark Twain wrote a book, Huckleberry Finn." The italics (or quotation marks, if you're still in thrall to the AP Stylebook) will do the job for you.