Hobos are by no means homeless people. Where the phrase 'hobo' originated from is unknown, but most historiand agree that it comes from the phrase 'ho boy' or a traveling man who would ho your crops for money. By definition a hobo is someone who travels around the country, train hopping, looking for work. If he's not working, then he's just a traveler, or a tramp.
Some pretty famous hobos were: Mark Twain, R. Crumb, and Tom Waits. Hardly just homeless people.
Train-hopping is one of the last great American adventures and there are still a few brave souls that realize this today. Prominent in the western half of continental US, it is rare to find a hobo east of the Mississippi.