derivable vs dubious

derivable

adj
  • able to be derived, deducible 

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. 

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