bad apple vs benign

bad apple

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

benign

adj
  • Not harmful to the environment. 

  • Kind; gentle; mild. 

  • Not posing any serious threat to health; not particularly aggressive or recurrent. 

  • mild and favorable 

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