familiarity vs proficiency in

familiarity

noun
  • Undue intimacy; inappropriate informality, impertinence. 

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

  • The state of being extremely friendly; intimacy. 

  • An instance of familiar behaviour. 

proficiency in

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