It's possible you're thinking of a related suffix like "-credo", which is used in words like "creed" and "credo" meaning "a statement of belief or principle".
There are also words like "incredible", "credible", and "accredit" which include a root related to belief and trust, but these are not formed by the suffix "-cred".
If you have a specific word in mind, please provide it and I can help you understand its formation.