adamant vs unvacillating

adamant

adj
  • Firm; unshakeable; unyielding; determined. 

  • Very difficult to break, pierce, or cut. 

noun
  • An embodiment of impregnable hardness. 

  • An imaginary rock or mineral of impenetrable hardness; a name given to the diamond and other substances of extreme hardness. 

unvacillating

adj
  • Not vacillating; firm, decided. 

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