According to sculptor Henry Sibson's chronicle, he worked on the Paris cathedral's renovation in the 1820s and met a stone carver named Trajan who was employed by a government studio foreman known only as Le Bossu, or "the hunchback". Glew searched for other references to corroborate the account and found Trajan listed as a professional carver in the 1833 Almanach de Paris, indicating that Le Bossu was probably also listed under his real name.
Hugo wrote his book at the same time period as Trajan's and Le Bossu's employment, and there's a good chance he knew of them, if he didn't know them personally. His character Valjean in "Le Miserable" was originally named "Trajean", so he could have based him on Trajan, after using Le Bossu as the basis for Quasimodo in the earlier book.
Reuters article.
