cop out vs renege

cop out

verb
  • To plead guilty and ask for mercy. 

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

renege

verb
  • To break a promise or commitment; to go back on one's word. 

  • In a card game, to break one's commitment to follow suit when capable. 

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