relinquish vs retain

relinquish

verb
  • To metaphorically surrender, yield control or possession. 

  • To give up, abandon or retire from something. To trade away. 

  • To let go (free, away), physically release. 

  • To accept to give up, withdraw etc. 

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