Noun. Slang word for money, especially that obtained
by criminal, illegal, or generally shady practices, e.g. selling
drugs, prostitution, slave trading. Can also mean a pay check while working
as an illegal immigrant. Used first by people in the black market and the Mafia.
Additionally, To 'give someone the mudsack' generally means to pay someone for doing something sneaky
for you that you didn't want to do yourself.
Jones: "So, Tommy, did you bring me the mudsack?"
Tommy: "Oh man! Jeez, I was too busy running away
from the cops to pick it up!"