Finger man by Raymond Chandler

I don't know if I should call it a short story or a short book... it has 55 pages in my edition. Nice anyway. Lots of action, told in the first person by Marlowe, few descriptions now and then just to create the atmosphere or to give a good sense of where they are. I mean, writers sometimes add so many descriptions, useless to the story, of every angle of the street and of every person met on the street, and a 55-pages-long story would have become a 150-pages-long book. It's a nice reading, so easy to imagine it in your mind like a noir film. Strangely I did not give Marlowe any actor's face, and I'm glad of it, but I couldn't help picture the scenes as if I was seeing a noir film.
The story: Lou, a little criminal, asks Marlowe a favor, to be a sort of bodyguard for him while he wins at the roulette. He's sure of it, he once owned it and says he knows how it works. Unable to change his mind, Marlowe goes, but he's knocked off and Lou is killed. Not for the money, though, but victim of a plot to stop both him and Marlowe from testifying against something like a man working for a corrupt politician, or whatever. When Marlowe was hit on the head, his gun was stolen and used to kill Lou, but there is who believes him: the chief of police (I think he was). They manage to save his alibi: a taxi-driver he had spoken to that night. The bad guys had gotten to him first, but they arrive on time to help him. He had been very scared but they had made the mistake of threatening to take away his little girl, so he got his rifle against them, and was fighting when Marlowe and his ally arrived to help. The ending is less thrilling than I expected, but well described and captivating enough. He goes to talk to the boss. Unable now to have Marlowe charged with Lou's murder, the boss wants to throw it upon Canales, the man the money were 'stolen' from, but he comes for revenge. He can only wound one of the boss Frank Dorr's men before being killed, but at that point it all ends with Marlowe hastily calling the police to the place while the redhead girl who had been forced to help them runs away undisturbed. It was well-written, I liked it enough. Sure, none of these old books are something I'd like to read again and again, but this one time was enjoyable enough. There's only one thing: the title. Why finger-man? What does it mean?