centennium vs millennium

centennium

noun
  • Synonym of century: A period of 100 years. 

millennium

noun
  • A period of time consisting of one thousand years. 

  • A period of universal happiness, peace or prosperity; a utopia. 

  • The period of one thousand years during which Christ will reign on earth (according to Millenarianist interpretations). 

  • The year in which one period of one thousand years ends and another begins, especially the year 2000. 

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