credence
/ˈkrē-dᵊn(t)s/
noun
mental acceptance as true or real
credibility
credentials —used in the phrase letters of credence
give credence to gossip
lends credence to the theory
noun phrase
a formal document attesting to the power of a diplomatic agent to act for the issuing government —called also letters of credence
idiom
to believe —usually used in negative statements