cave in vs disapprove

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. 

disapprove

verb
  • To refuse to approve; reject. 

  • To have or express an unfavorable opinion. 

  • To condemn; to consider wrong or inappropriate; used with of. 

  • She disapproves of rap music because of its sometimes aggressive lyrics. 

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