indubitable vs unchallenged

indubitable

noun
  • That which is indubitable. 

adj
  • clearly true; providing no possibility of doubt. 

unchallenged

adj
  • Lacking experience due to lack of challenges; untested. 

  • Not having any challengers. 

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