conviction vs credo

conviction

noun
  • A firmly held belief. 

  • A judgement of guilt in a court of law. 

  • The state of being wholly convinced. 

  • The state of being found or proved guilty. 

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 conviction and credo occurred in a corpus of books? (source: Google Ngram Viewer )