cop out vs pass the buck

cop out

verb
  • To avoid or shirk, either by failing to perform, or by performing in a grossly insufficient, negligent, or superficial manner. 

  • To plead guilty and ask for mercy. 

pass the buck

verb
  • To transfer responsibility or blame from oneself onto another; to absolve oneself of concern for a given matter by claiming to lack authority or jurisdiction. 

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