question vs question mark

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. 

question mark

noun
  • A state of doubt or uncertainty. 

  • An enigmatic, inscrutable, or mysterious person or thing; an enigma, a riddle. 

  • The punctuation mark "?", used at the end of a sentence to indicate a question. 

  • Polygonia interrogationis, a North American nymphalid butterfly with a silver mark on the underside of its hindwing resembling a question mark (sense 1). 

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