Tramp means to walk or stomp heavily. Your midnight tramp to the kitchen for milk and cookies doesn't thrill your downstairs neighbors.
Tramp comes from the German trampen, for "stamp." If you walk heavily, people will say you tramp, but if you're going on a tramp, that means you're going for a long walk or hike. If someone calls you a tramp, they either mean you're a slut or a hobo — each meaning comes vagrant, or wanderer, and the low-life behaviors associated with vagrants.