impotent vs redoubtable

impotent

noun
  • a man who has erectile dysfunction 

  • an impotent or powerless person 

adj
  • lacking physical strength or vigor; weak 

  • incapable of sexual intercourse, often because of an inability to achieve or sustain an erection, having impotentia coeundi 

  • lacking in power, as to act effectively; helpless 

  • sterile 

redoubtable

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

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