doubt vs questioning

doubt

noun
  • Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty. 

verb
  • To be undecided about; to lack confidence in; to disbelieve, to question. 

questioning

noun
  • The act of challenging, wondering, and doubting. 

  • Interrogation. 

  • The action of asking questions; a survey; an inquiry. 

adj
  • Unsure of one's sexual orientation and/or gender identity. 

  • Characterized by questions, inquisitiveness, doubt, or wonder. 

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