harbor vs retain

harbor

verb
  • To provide a harbor or safe place for. 

  • To take refuge or shelter in a protected expanse of water. 

  • To drive (a hunted stag) to covert. 

  • To hold or persistently entertain in one's thoughts or mind. 

noun
  • A sheltered expanse of water, adjacent to land, in which ships may anchor or dock, especially for loading and unloading. 

  • Any place of shelter. 

  • A mixing box for materials. 

  • A harbor, even if it is a little harbor, is a good thing, since adventurers come into it as well as go out, and the life in it grows strong, because it takes something from the world, and has something to give in return - Sarah Orne Jewett 

retain

verb
  • To hold secure. 

  • 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 keep in possession or use. 

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