code name vs designation

code name

noun
  • A name used to clandestinely identify somebody or something, either for military or espionage purposes, or for commercial confidentiality. 

designation

noun
  • That which designates; a distinguishing mark or name; distinctive title; appellation. 

  • Selection and appointment for a purpose or office; allotment; direction. 

  • signification, meaning, for example of a word or phrase. 

  • An act or instance of designating; a pointing out or showing; indication. 

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