redoubtable vs tenacious

redoubtable

adj
  • Eliciting respect or fear; imposing; awe-inspiring. 

tenacious

adj
  • Unwilling to yield or give up; dogged. 

  • Having a good memory; retentive. 

  • Holding together; cohesive. 

  • Clinging to an object or surface; adhesive. 

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