While Silver (and the Walt Disney animated movie) is correct in stating that the name can mean “partially form”, Victor Hugo, the author of the novel *The Hunchback of Notre Dame*, actually offers two explanations in his story for why Claude Frollo (who, by the way, was NOT responsible for the death of Quasi’s mother, as depicted in the Disney movie, but who actually, in an act of compassion, had rescued the infant Quasi from a group of old women who were tormenting the deformed baby) named Quasi as he did:
"He baptized his adopted child and named him Quasimodo, either in order to commemorate the day on which he found him or because he wished to express by this name the degree to which the poor little creature was incomplete and imperfectly molded."
The day on which Quasi was rescued by Frollo was the first Sunday after Easter – which is called "Quasimodo Sunday" in France on account of the opening words to the Introit of the Roman Catholic Mass celebrated on that day: "Quasi modo geniti infantes, rationabiles, sine dolo lac concupiscite." In translation, this is: "As newborn [i.e. "partially formed"] babes, desire the rational milk without guile." This is a reference to new converts to the Roman Catholic faith, who have subsequently been "saved" -- which is also what Claude Frollo perceived Quasi to be through his rescuing, adoption, and baptizing of Quasi.