helpless vs nonconvincing

helpless

adj
  • Uncontrollable. 

  • Unable to defend oneself. 

  • Unable to act without help; needing help; feeble. 

  • Lacking help; powerless. 

nonconvincing

adj
  • unconvincing 

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