dispose of vs retain

dispose of

verb
  • To have available, or at one's disposal. 

  • To transfer to another's control. 

  • To get rid of. 

  • To arrange in an orderly way. 

  • To deal with conclusively with a threat or a difficult situation. 

retain

verb
  • To keep in possession or use. 

  • To employ by paying a retainer. 

  • To hold back (a pupil) instead of allowing them to advance to the next class or year. 

  • To keep in one's pay or service. 

  • To hold secure. 

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