not approved vs sub rosa

not approved

sub rosa

noun
  • Covert surveillance video used to catch workers’ compensation applicants and show that they are in fact not injured. 

adj
  • Carried out secretly or confidentially. 

adv
  • In secret or covertly; privately, confidentially. 

How often have the words not approved and sub rosa occurred in a corpus of books? (source: Google Ngram Viewer )