1930s; earliest use found in Raymond Chandler (1888–1959), detective novelist. Popularized by the title of Raymond Chandler's novel The Big Sleep and the 1946 film adaptation of the same name.
Definition of big sleep in US English:
big sleep
noun
US slang
(Usually with the) death.
Origin
1930s; earliest use found in Raymond Chandler (1888–1959), detective novelist. Popularized by the title of Raymond Chandler's novel The Big Sleep and the 1946 film adaptation of the same name.