*TRAMP. In the U.S.A. 'there are three types of the genus vagrant: the hobo, the tramp, and the bum. The hobo works and wanders, the tramp dreams and wanders, and the bum drinks and wanders,' Dr. Ben L. Reitman; St. John Tucker, however, says, 'A hobo is a migratory worker. A tramp is a migratory non-worker. A bum is a stationary non-worker.' And Godfrey Owen cites an experienced 'knight of the road' as saying that 'Bums loafs and sits. Tramps loafs and walks. But a hobo moves and works, and he's clean.'
--Eric Partridge, The Wordsworth Dictionary of the Underworld.