Mafia vs gangland

Mafia

name
  • A party game modelling a conflict between an informed minority (the mafia) and an uninformed majority (the innocents). Each player is secretly assigned a role within one of these teams, and the innocents attempt to identify the mafia members before they are all "murdered". 

  • The international criminal organization of Sicilian origin operating in Italy and the United States. 

  • Any other specific organized crime syndicate operating internationally in high-level organized crime; often with a modifying adjective, such as a nationality. 

gangland

noun
  • The underworld of organized crime. 

How often have the words Mafia and gangland occurred in a corpus of books? (source: Google Ngram Viewer )