nurture vs retain

nurture

verb
  • To nourish or nurse. 

  • To encourage, especially the growth or development of something. 

noun
  • That which nourishes; food; diet. 

  • The act of nourishing or nursing; tender care 

  • The environmental influences that contribute to the development of an individual (as opposed to "nature"). 

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 nurture and retain occurred in a corpus of books? (source: Google Ngram Viewer )