fall apart vs happen

fall apart

verb
  • To be emotionally in crisis. 

  • To disintegrate, to break into pieces. 

happen

verb
  • To encounter by chance. 

  • To do or occur by chance or unexpectedly. 

  • To occur or take place. 

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