bad apple vs moral

bad apple

noun
  • A person who is not wholesome, honest, or trustworthy, especially one who has an adverse influence on others. 

moral

noun
  • Moral practices or teachings: modes of conduct. 

  • The ethical significance or practical lesson. 

verb
  • To moralize. 

adj
  • Probable but not proved. 

  • Of or relating to principles of right and wrong in behaviour, especially for teaching right behaviour. 

  • Conforming to a standard of right behaviour; sanctioned by or operative on one's conscience or ethical judgment. 

  • Capable of right and wrong action. 

  • Positively affecting the mind, confidence, or will. 

How often have the words bad apple and moral occurred in a corpus of books? (source: Google Ngram Viewer )