foray vs irruption

foray

noun
  • A sudden or irregular incursion in border warfare; hence, any irregular incursion for war or spoils; a raid. 

  • A brief excursion or attempt, especially outside one's accustomed sphere. 

verb
  • To participate in a foray. 

  • To do or attempt something outside one's typical area of expertise. 

irruption

noun
  • The action of irrupting or breaking into; a violent entry or invasion; an inbreaking; an intrusion. 

  • An abrupt increase in the size of a movement or organization. 

  • An abrupt increase of an animal population. 

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