fend off vs push back

fend off

verb
  • To defend against; to repel with force or effort 

  • To prevent (a vessel) from running against anything with too much violence. 

push back

verb
  • To refute or argue against a position or an accusation; to express one's own view on a situation. 

  • To postpone. 

  • To summarily expel asylum seekers, especially in violation of the principle of non-refoulement. 

  • Used other than figuratively or idiomatically: see push, back. 

How often have the words fend off and push back occurred in a corpus of books? (source: Google Ngram Viewer )