Definition of Wise Guy
Originally, wise guy was another Mafia nickname like goodfella, made man, made guy, man of honor and so forth. In other words, a wise guy was a man who the American or Sicilian Mafia had officially inducted into their ranks.
In America, during their halcyon days, the Mafia ran much of the action. They ran it on the up-and-up in places like Las Vegas and Atlantic City, and they ran criminal betting enterprises in places like New York and Chicago.
So back in the day, many bookies were also wise guys, and there was some synergy between the phrase ‘wise guy’ and the notion of the professional bettor. So wise guy became synonymous with that, in Las Vegas in particular.
Because of that, today the term wise guy is still very much a part of the common betting vernacular. When we use it, we’re usually using it to refer to someone who is successful in the industry to the point of making a career out of it.
The criminal aspect is gone. For the most part, all wise guys today are legit. And not all wise guys are bookies. Many of them work for the casinos providing services, and some sell their advice directly to the general betting public.