break up vs take a rain check

break up

verb
  • Of a conversation, to cease to be understandable because of a bad connection; of a signal, to deteriorate. 

  • To end a (usually romantic or sexual) relationship with each other. 

  • To dissolve; to part. 

  • To break or separate into pieces. 

  • Become disorganised 

  • Of a school, to close for the holidays at the end of term. 

  • be or cause to be overcome with laughter 

  • To end a (usually romantic or sexual) relationship. 

  • To stop a fight; to separate people who are fighting. 

  • To cut or take to pieces for scrap. 

  • To break or separate into pieces; to disintegrate or come apart. 

  • To upset greatly; to cause great emotional disturbance or unhappiness. 

take a rain check

verb
  • In social interactions, to request a deferral of an invitation. To "take a rain check" is a polite way to turn down an engagement, usually with the implication that one is simply postponing it and another time might be acceptable. 

  • To request or accept a rain check (an agreement from a merchant to honor a special offer, temporarily unavailable, after the expiration date). 

How often have the words break up and take a rain check occurred in a corpus of books? (source: Google Ngram Viewer )