acquaintancy vs familiarity

acquaintancy

noun
  • acquaintanceship 

familiarity

noun
  • Close or habitual acquaintance with someone or something; understanding or recognition acquired from experience. 

  • Undue intimacy; inappropriate informality, impertinence. 

  • The state of being extremely friendly; intimacy. 

  • An instance of familiar behaviour. 

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