extermination vs frankpledge

extermination

noun
  • The act of exterminating; total destruction or eradication 

  • Elimination. 

frankpledge

noun
  • A form of collective suretyship and punishment under English law among the members of a tithing. 

  • A decener: a member of a tithing bound in frankpledge. 

  • Any group so similarly answerable for the conduct of all its members and liable for collective punishment. 

  • The tithing itself. 

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