Like all of us, nursery rhymes hold their own dirty secrets. London librarian Chris Roberts’ Heavy Words Lightly Thrown: The Reason Behind the Rhyme offers nearly 200 pages of historical record that examines many of the classics’ not-all-that-suitable-for-children backstories. Roberts traces Tweedledum and Tweedledee back to a 1725 feud between composers Handel and Bononcini (and extends the allegory to the row between Blur and Oasis), details an affair between King James I and the Duke of Buckingham, and calls Lewis Carroll a “four-eyed cleric.” Despite its lighthearted subject matter, Roberts’ book is painstakingly researched, though not so scholarly as to put off casual readers. Still, in his preface to the U.S. edition of the book, the self-admittedly “very British” Roberts writes that he was concerned that his references would fly over the heads of his American audience. So he wrote up a glossary. The asterisks that lead readers there prove to be a little distracting, but the additional insight offered takes the edge off: “One saucy explanation of this rhyme,” he writes in his examination of “Jack and Jill,” “is that ‘up the hill to fetch a pail of water’ is actually a euphemism for having sex, and that ‘losing your crown’ means losing your virginity.” Roberts reads at 7 p.m. Monday, Sept. 12, at Olsson’s Books & Records, 418 7th St. NW. Free. (202) 638-7610. (Mike Kanin)