ambush vs warning

ambush

verb
  • To station in ambush with a view to surprise an enemy. 

  • To attack by ambush; to waylay. 

noun
  • The act of concealing oneself and lying in wait to attack by surprise. 

  • The concealed position or state from which a surprise attack is launched. 

  • An attack launched from a concealed position. 

  • The troops posted in a concealed place, for attacking by surprise; those who lie in wait. 

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 ambush and warning occurred in a corpus of books? (source: Google Ngram Viewer )