questioning vs unbelief

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. 

unbelief

noun
  • An absence (or rejection) of belief, especially religious belief 

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