dubious vs incontestable

dubious

adj
  • Arousing doubt; questionable; open to suspicion. 

  • In disbelief; wavering, uncertain, or hesitating in opinion; inclined to doubt; undecided. 

  • Generally considered imprecise or wrong, but not totally unplayable. 

incontestable

adj
  • Not contestable; indisputable; certain 

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