Walter Mitty is a fictional character in James Thurber’s short story The Secret Life of Walter Mitty, first published in The New Yorker in 1939, and in book form in My World and Welcome to It in 1942. It was made into a firm in 1947. Mitty is a meek, mild man with a vivid fantasy life. He imagines himself a wartime pilot, an emergency-room surgeon, and a devil-may-care killer.
The term ‘Walter Mitty’ has come to be used to refer to an ineffectual dreamer, a person who indulges in fantastic daydreams but never actually achieves anything.