ditch vs retain

ditch

verb
  • To deliberately not attend classes; to play hookey. 

  • To dig ditches around. 

  • To dig ditches. 

  • To throw into a ditch. 

  • To discard or abandon. 

  • To deliberately crash-land an airplane on water. 

noun
  • A trench; a long, shallow indentation, as for irrigation or drainage. 

  • A raised bank of earth and the hedgerow on top. 

retain

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

  • To employ by paying a retainer. 

  • To keep in one's pay or service. 

  • To keep in possession or use. 

  • To hold secure. 

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