cave in vs submit

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. 

submit

verb
  • To yield or give way to another. 

  • To yield (something) to another, as when defeated. 

  • To win a fight against (an opponent) by submission. 

  • To enter or put forward for approval, consideration, marking etc. 

  • To subject; to put through a process. 

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