cave in vs subside

cave in

verb
  • To collapse inward or downward. 

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

noun
  • The act of relenting. 

  • The location where something has caved in. 

  • The act of something collapsing or caving in. 

subside

verb
  • To fall downward; to become lower; to descend; to sink. 

  • To cease talking. 

  • To sink or fall to the bottom; to settle, as lees. 

  • To fall into a state of calm; to be calm again; to settle down; to become tranquil; to abate. 

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