How fitting that the man often credited with saying “a lie can travel halfway around the world while the truth is still putting on its shoes” most likely did not invent the phrase.

Commonly attributed to Mark Twain, that quotation instead appears to be a descendant of a line published centuries ago by the satirist Jonathan Swift. Variants emerged and mutated over time until a modern version of the saying was popularized by a Victorian-era preacher, according to Garson O’Toole, a researcher who, like Twain, prefers a pseudonym.

Seven years ago, Mr. O’Toole started Quote Investigator, a popular website where he traces the origins of well-known sayings. This month, he published “Hemingway Didn’t Say That: The Truth Behind Familiar Quotations,” a book in which he collected and updated many of the posts from his site and offers new theories on how misquotations form.

“When I started off, it was mysterious exactly where these misquotations were coming from, and it was interesting that sometimes you could find these clues that pointed to how they may have originated,” said Mr. O’Toole, an alias for Gregory F. Sullivan, a former teacher and researcher in the Johns Hopkins computer science department who now spends his time writing.