This bookkeeper is deaf. It was considered an occupational benefit, and the main reasonwhy he got the job in the first place, since it was assumed that a deaf bookkeeper would not be able to hear anything he'd ever have to testify about in court.
When the Godfather goes to shakedown the bookkeeper about his missing $10 million, he brings along his attorney, who knows sign language. The Godfather asks the bookkeeper: "Where is the 10 million bucks you embezzled from me?"
The attorney, using sign language, asks the bookkeeper where the 10 million dollars is hidden. The bookkeeper signs back: "I don't know what you are talking about."
The attorney tells the Godfather: "He says he doesn't know what you're talking about."
That's when the Godfather pulls out a 9 mm pistol, puts it to the bookkeeper's temple, cocks it, and says: "Ask him again!"
The attorney signs to the underling: "He'll kill you for sure if you don't tell him!"
The bookkeeper signs back: "OK! You win! The money is in a brown briefcase, buried behind the shed in my cousin Enzo's backyard in Queens!"
The Godfather asks the attorney: "Well, what'd he say?"
The attorney replies: "He says you don't have the guts to pull the trigger."