certain vs questioning

certain

det
  • Having been determined but not specified. 

adj
  • Unfailing; infallible. 

  • Known but not specifically named; indeterminate; indefinite; one or some; sometimes used independently as a noun, and meaning certain persons; see also "one". 

  • Fixed or stated; regular; determinate. 

  • Not to be doubted or denied; established as a fact. 

  • Sure, positive, not doubting. 

  • Actually existing; sure to happen; inevitable. 

pron
  • Unnamed or undescribed members (of). 

questioning

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

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

noun
  • Interrogation. 

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

  • The act of challenging, wondering, and doubting. 

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