hecatontarchy vs oligarchy

hecatontarchy

noun
  • A government of 100 rulers. 

oligarchy

noun
  • A state ruled by such a government. 

  • Those who make up an oligarchic government. 

  • A government run by only a few, often the wealthy. 

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