The Fabulous Clipjoint by Frederic Brown.
It's a murder mystery, written in 1947, set in Chicago, and with some of the characters as 'carneys', who have a language of their own.
For example, when one character who runs a sideshow where customers throw baseballs at dummy milk bottles to win prizes, but has to go away for a while, he asks his friend if he would like to take over while he is gone. HIs friend answers:
"Hell, yes. I'm sloughed here and ten to one I'll be sloughed in Springfield. And if Jake gets a chance to use the blow after that, let him get a cooch. What cut you want?"
I had no idea what he was talking about, but fortunately Brown explains it all later in the book. An interesting book for several reasons.