beat one's meat vs bop the bishop

beat one's meat

verb
  • To masturbate by stroking or rubbing one's penis. 

  • To waste time; to engage in an unproductive activity. 

bop the bishop

verb
  • To masturbate (male). 

How often have the words beat one's meat and bop the bishop occurred in a corpus of books? (source: Google Ngram Viewer )