It is used here in the UK to roughly mean something that happens as a result of a previous action (often but not always unwittingly) .As for knock-off it has a myriad of meanings,

to leave work--- "I knocked off at 4 today"
rapidly compose------- "Iknocked off a letter to my mum"
deduct -----------"I'll knock off £5 from your bill"
stolen -------"everything you could see in the room was knocked off"
spanking the monkey!!!----------"alone in his room, he quietly knocked one off "
to be sexually intimate with--------"unbeknown to his wife Bill had been knocking off the woman next-door"


the Duncster ( lethal bones)

the Duncster