fraternization vs joint effort

fraternization

noun
  • any type of disallowed, supposedly unethical and unprofessional, social or intimate contact between employees, especially between different gender, class or rank. 

  • The act of fraternizing or uniting as brothers. 

  • Having a friendly relationship with the enemy. 

joint effort

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