cave in vs rebuff

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. 

rebuff

verb
  • To refuse; to offer sudden or harsh resistance; to turn down or shut out. 

  • To buff again. 

noun
  • Repercussion, or beating back. 

  • He was surprised by her quick rebuff to his proposal. 

  • A sudden resistance or refusal. 

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