happen vs spring out

happen

verb
  • To occur or take place. 

  • To do or occur by chance or unexpectedly. 

  • To encounter by chance. 

spring out

verb
  • To emerge or arise. 

  • Used other than figuratively or idiomatically: see spring, out. 

  • To break out; to escape. 

  • To spend the season of spring in outdoor pursuits such as camping. 

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