for keeps vs forevermore

for keeps

prep
  • With an agreement or intention to retain what one gains or receives. 

  • Permanently, so that one can keep something indefinitely. 

  • With a strong competitive resolve to win or succeed, as in sports or business. 

forevermore

adv
  • At any or all times in the future; forever 

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