clue vs warning

clue

noun
  • An object or a kind of indication which may be used as evidence. 

  • Information which may lead one to a certain point or conclusion. 

  • Insight or understanding ("to have a clue [about]" or "to have clue". See have a clue, clue stick) 

verb
  • To provide with a clue. 

  • To provide someone with information which he or she lacks (often used with "in" or "up"). 

warning

noun
  • Something spoken or written that is intended to warn. 

  • The action of the verb warn; an instance of warning someone. 

intj
  • Used to warn of danger in signs and notices. 

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