Down and out in America? Sorry to hear that! That makes you officially a bum. It's what comes from hanging around, doing nothing, from the German bommeln, "to loiter" and the bummler, "an idler or loafer." You got your bad name from nativists who associated you and your countrymen with bumming or "sponging" off others during the first major wave of German immigration in the 1850s.
The language never gave you a break. Things on the bum (c.1889) simply didn't work properly. And when you got the bum's rush, they picked you up by the seat of your pants and threw you off the premises.
That's what you call a bummer, "a real bad experience" (c.1960s). Some think the bummer's origins derive from the famed 18th century organ maker, Johann Jakob Bommer, "whose instruments were so admired they created the expression ‘It's a real Bommer.’" Unfortunately, so's the explanation.
No need to be bummed out (c. 1970) about it "depressed or dispirited." During the great depression, many homeless often rode the rails by clinging to the hardware or trucking between the wheels of a freight train. Trucking became synonymous with leaving or moving on and it blossomed fully during the `60s, thanks to Robert Crumb, creator of Fritz the Cat. So rather than just hanging around, you too might just want to keep on truckin!