In the Mafia's infancy, the modus operandi was to shake down local merchants for “protection.” This code word simply meant that if the shopkeeper refused to pay the mobster, the mobster would have the shop trashed … or worse. The early Mustache Pete's preyed solely on their own fellow immigrants, rarely venturing outside the area to shakedown other groups. But as their influence expanded the extortion racket was brought to other neighborhoods.
The Mafia makes a lot of its money from imposing a “street tax” on independent criminals operating in its territory. Drug dealers have long been a favorite target. Why deal the drugs yourself when you can simply shakedown a dealer? It's less work and less risk. The street tax is usually applied to bookmakers, pimps, con men, and thieves, but can also include other criminals, as well as up and coming mob associates.
The term that the Mafia used to get money from local neighborhood merchants was “a little to wet my beak.” That was enough to let the shopkeepers know that if they didn't kick up some of their hard-earned money, then retribution would be harsh.