encroachment vs irruption

encroachment

noun
  • An entry into a place or area that was previously uncommon; an advance beyond former borders; intrusion; incursion. 

  • That which is gained by such unlawful intrusion. 

  • An intrusion upon another's possessions or rights; infringement. 

  • An unlawful diminution of the possessions of another. 

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 encroachment and irruption occurred in a corpus of books? (source: Google Ngram Viewer )