coward vs yellow dog

coward

noun
  • A person who lacks courage. 

adj
  • Cowardly. 

  • Borne in the escutcheon with his tail doubled between his legs. 

yellow dog

noun
  • An item or person of low value. 

  • Used other than figuratively or idiomatically: see yellow, dog. 

  • A Carolina dog. 

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