drag one's feet vs retard

drag one's feet

verb
  • To intentionally stall, to delay, to obstruct. 

  • To procrastinate, put off; to dawdle, avoid, or make progress slowly and reluctantly. 

retard

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

  • To put off; to postpone. 

  • To decelerate; to slow down. 

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 drag one's feet and retard occurred in a corpus of books? (source: Google Ngram Viewer )