ulterior vs undercover

ulterior

adj
  • Being intentionally concealed so as to deceive. 

  • Situated beyond, or on the farther side. 

  • Beyond what is obvious or evident. 

undercover

adj
  • Performed or happening in secret. 

  • Employed or engaged in spying or secret investigation. 

verb
  • To provide too little coverage. 

noun
  • A person who works undercover. 

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