code of belief vs credo

code of belief

credo

noun
  • A statement of a belief or a summary statement of a whole belief system; also (metonymically) the belief or belief system itself. 

  • The liturgical creed (usually the Nicene Creed), or a musical arrangement of it for use in church services. 

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