E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Sleep like a Top.
When peg-tops and humming-tops are at the acme of their gyration they become so steady and quiet that they do not seem to move. In this state they are said to sleep. Soon they begin to totter, and the tipsy movement increases till they fall. The French say, Dormir comme un sabot, and Mon sabot dort. (See SIMILES.)