deadbolt vs retain

deadbolt

verb
  • To fasten or secure with a deadbolt. 

noun
  • A kind of lock in which the bolt (moving portion) is held in position by the cylinder rather than by a spring and so cannot be retracted except by turning the cylinder. 

  • The part of the lock which is moved when the key is engaged. 

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