shell out vs spring for

shell out

verb
  • To pay money, to disburse; especially, to pay a great deal of money. 

  • To use a program's "shell escape" function to execute an unrelated command or to invoke a subsidiary, interactive shell. 

spring for

verb
  • To pay for; to offer money. 

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