Land of Nod
Land of Nod is the name of the land, to "the east of Eden," to which Cain was banished after murdering his brother Abel in the first book of the Bible. The word "nod" means "wandering."
The term has more recently been associated with being asleep and was supposedly first used in this context in print by Jonathan Swift in his A Complete Collection of Genteel and Ingenious Conversation (1738).