Q: Where did the expression “Catch-22” come from?
A: Catch-22 is the title of Joseph Heller's 1953 novel about bomber crews during World War 2. It refers to a paradox: attempting to escape makes escape impossible. In the novel, bomber crew members apply for exemption from highly dangerous missions on the grounds of insanity. Applications are rejected, since anyone who would apply for exemption from going on these missions must be sane. The expression “damned if you do, and damned if you don't” covers the situation.
Today the expression is often misused to mean any difficult situation.