a hobo is an itinerant worker, a career which sprang up during the depression. A hobo, unlike a bum or a tramp, is more than willing to work, but mostly for a short duration, as their main impetus is travel, the love of the journey above the actual destination. A bum is stationary, feeding off of those unfortunate enough to cross his path; a hobo merely travels from town to town, finding work when he can, but only for the sake of financing his next adventure. NEVER call a hobo a bum...they'll kick your sorry no-bo ass!
"When I first started hobo'in,
I took a freight train to be my friend
-John Lee Hooker