mystery vs question

mystery

noun
  • A religious truth not understandable by the application of human reason alone (without divine aid). 

  • Someone or something with an obscure or puzzling nature. 

  • Something secret or unexplainable; an unknown. 

  • A particular event or series of events in the life of Christ. 

  • A sacrament. 

  • A secret religious celebration, admission to which was usually through initiation. 

  • A craft, art or trade; specifically a guild of craftsmen. 

question

noun
  • A doubt or challenge about the truth, accuracy, or validity of a matter. 

  • A subject or topic for consideration or investigation. 

  • A sentence, phrase or word which asks for information, reply or response; an interrogative. 

  • A proposal to a meeting as a topic for deliberation. 

verb
  • To ask a question or questions; inquire or seek to know; examine. 

  • To ask questions of; to interrogate; to ask for information. 

  • To raise doubts about; have doubts about. 

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