I've heard tyro before as a synonym for newbie, but damned if I can remember the origin.
Speaking of dams, ever hear the phrase 'not worth a tinker's dam'? Continuing on the stuff about tinkers, the 'dam' was a clay patch put into place over a hole in a pan. Molten tin was then applied to the other side to form the proper patch, and then the clay was knocked off. Obviously, not worth anything -- hence the phrase.
American hobos and tramps tend to be a very curious, very different breed from Roma/travelers. I remember hearing somewhere -- can't recall where -- that most hobos loathe traveler bands and avoid them like the plague.