truthful vs undercover

truthful

adj
  • Honest, and always telling the truth. 

  • Accurately depicting what is real. 

undercover

verb
  • To provide too little coverage. 

noun
  • A person who works undercover. 

adj
  • Performed or happening in secret. 

  • Employed or engaged in spying or secret investigation. 

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