CoR vs chieftain

CoR

noun
  • European Committee of the Regions, the European Union's assembly of local and regional representatives. 

  • Confederation of Regions Party of Canada, Canadian political party. 

  • College of Radiographers, a charitable subsidiary of the Society of Radiographers. 

chieftain

noun
  • A leader of a group. 

  • A leader of a clan or tribe. 

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