moron vs retard

moron

noun
  • A stupid person; an idiot; a fool. 

retard

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

  • Retardation; delay. 

  • A slowing down of the tempo; a ritardando. 

verb
  • To put off; to postpone. 

  • To decelerate; to slow down. 

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

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