push back vs retard

push back

verb
  • To postpone. 

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

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

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

retard

verb
  • To put off; to postpone. 

  • To decelerate; to slow down. 

  • To keep delaying; to continue to hinder; to prevent from progressing. 

noun
  • Retardation; delay. 

  • A slowing down of the tempo; a ritardando. 

  • A person or being who is extremely stupid or slow to learn. 

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