cave in vs defend

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. 

defend

verb
  • To support by words or writing; to vindicate, talk in favour of. 

  • To focus one's energies and talents on preventing opponents from scoring, as opposed to focusing on scoring. 

  • To attempt to retain a title, or attempt to reach the same stage in a competition as one did in the previous edition of that competition. 

  • To call a raise from the big blind. 

  • To ward off attacks against; to fight to protect; to guard. 

  • To make legal defence of; to represent (the accused). 

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