fraternization vs membership

fraternization

noun
  • The act of fraternizing or uniting as brothers. 

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

  • Having a friendly relationship with the enemy. 

membership

noun
  • The state of being a member of a group or organization. 

  • The body of members of an organization. 

  • The fact of being a member of a set. 

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