helter-skelter vs question mark

helter-skelter

noun
  • Confusion or turmoil. 

  • A helical fairground slide. 

adv
  • In confused, disorderly haste. 

adj
  • Carelessly hurried and confused. 

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 helter-skelter and question mark occurred in a corpus of books? (source: Google Ngram Viewer )