cave in vs quit

cave in

verb
  • To relent; to grant approval against one's initial will. 

  • To collapse inward or downward. 

noun
  • The act of relenting. 

  • The location where something has caved in. 

  • The act of something collapsing or caving in. 

quit

verb
  • To release from obligation, accusation, penalty, etc.; to absolve; to acquit. 

  • To leave (a place). 

  • To stop, give up (an activity) (usually + gerund or verbal noun). 

  • To resign from (a job, office, position, etc.). 

  • To close (an application). 

  • To set at rest; to free, as from anything harmful or oppressive; to relieve; to clear; to liberate. 

  • To abandon, renounce (a thing). 

adj
  • Released from obligation, penalty, etc; free, clear, or rid. 

noun
  • Any of numerous species of small passerine birds native to tropical America. 

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