riffraff vs yellow dog

riffraff

noun
  • Sweepings; refuse. 

  • The rabble; crowds; the common people. 

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 riffraff and yellow dog occurred in a corpus of books? (source: Google Ngram Viewer )