The title is the name, or rather nickname, of a character in the movie, the wealthy Jeff Lebowski. But it's also a reference to the Raymond Chandler novel, The Big Sleep. The Big Sleep, which was made into a very famous film starring Humphrey Bogart and Lauren Bacall in 1946, is one of Raymond Chandler's best known novels. Like The Big Lebowski, The Big Sleep is set in L.A. and features a dense and confusing mystery that needs to be solved by a lovable, hard-bitten antihero. The Coens said they were using this film as a model for tone and plot.