The title refers to a fictional bureaucratic stipulation that embodies illogical and immoral reasoning. The opening chapter of the novel was first published, in 1955, by New World Writing as Catch-18, but Heller's agent, Candida Donadio, asked him to change the title, to avert its confusion with Leon Uris's recently published Mila 18. The implications in Judaism of the number 18 — which refers to chai, meaning "alive", in Gematria — were relevant to Heller's somewhat greater emphasis on Jewish themes in early drafts of his novel.
Parallels among a number of character exchanges in the novel suggested the doubled-one title of Catch-11, but the 1960 release of Ocean's Eleven eliminated that. Catch-17 was rejected so as not to be confused with the World War II film Stalag 17, as was Catch-14, apparently because the publisher did not believe that 14 was a "funny number". Eventually, the title came to be Catch-22, which, like 11, has a duplicated digit, with the 2 also referring to a number of déjà vu-like events common in the novel.