The title is a reference to a fictional bureaucratic stipulation which embodies forms of illogical and immoral reasoning. The opening chapter of the novel was originally published in New World Writing as Catch-18 in 1955, but Heller's agent, Candida Donadio, requested that he change the title of the novel, so it would not be confused with another recently published World War II novel, Leon Uris's Mila 18. The number 18 has special meaning in Judaism (it means Alive in Gematria; see Chai) and was relevant to early drafts of the novel which had a somewhat greater Jewish emphasis.
The title Catch-11 was suggested, with the duplicated 1 paralleling the repetition found in a number of character exchanges in the novel, but because of the release of the 1960 movie Ocean's Eleven, this was also rejected. 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 feel 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.