Sorry for being pedantic, but since I was looking it up since I wasn't even sure of the correct spelling, I thought I'd share the result...
riffraff
n.
1. People regarded as disreputable or worthless.
2. Rubbish; trash.
[Late Middle English riffe raffe, from Middle English rif and raf, everything, one and all, rubbish, rabble, ultimately (if the expression was not coined in Middle English from elements of French origin and then borrowed by Middle French) from Middle French and Anglo-Norman rifraf, rif et raf, altogether, as in emporter rif et raf, to take away everything, probably a reduplicated formation from Middle French rifler, to plunder (from Old French to brush up against, scratch; see RIFLE2) and Middle French rafer, to remove or make off with forcefully (from Old French, of Germanic origin; akin to Middle Dutch rapen, to gather, collect, and Middle High German raffen, to snatch, rip off).]