retard vs stop over

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. 

stop over

verb
  • To interrupt one's journey for a short (sometimes overnight) stay; to stop off. 

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