expedite vs retard

expedite

verb
  • To accelerate the progress of. 

  • To perform (a task) fast and efficiently. 

  • To perform the duties of an expediter. 

adj
  • Expeditious; quick; prompt. 

  • Free of impediment; unimpeded. 

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 expedite and retard occurred in a corpus of books? (source: Google Ngram Viewer )