acquaint vs fill in

acquaint

verb
  • To furnish or give experimental knowledge of; to make (one) know; to make familiar. 

fill in

verb
  • To inform somebody, especially to supply someone missing or missed information. 

  • To substitute for somebody or something. 

  • To complete a form or questionnaire with requested information. 

  • To beat up; to physically assault. 

  • To fill; to replace material that is absent or has been removed. 

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