What is the difference between creed and credo? They seem to have the same definition in online dictionaries. Do they have different connotations?
They are interchangeable, but I think there are some subtleties that may or may not be important.
A creed is often a shared and established statement of belief. The Nicene Creed was established to be a statement of faith symbolizing a shared understanding of Christianity between believers.
Credo, or "I believe," tends to be a personal statement and is not necessarily bound by a group. My personal credo could be, "Bacon, always."
To me credo has a connotation of a personal belief. Almost a tagline. I think these are sometimes used light heartedly. jboneca's 'Always Bacon' is a fantastic example.
A creed to me implies a more formal statement of belief (church) or ethics (business). It carries more conviction. ex Assassins Creed , Nicene Creed, etc.
This is my opinion and reflects how I have experienced their uses. Research clearly supports jboneca's statement that creed is based on credo.