nobility vs plebs

nobility

noun
  • The quality of being noble. 

  • A noble or privileged social class, historically accompanied by a hereditary title; aristocracy. 

plebs

noun
  • The plebeian class of Ancient Rome. 

  • The common people, especially (derogatory) the mob. 

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