Originally With plural agreement: things to be believed; matters of faith; propositions forming or belonging to a system. Also in singular (credendum): one such thing, an article of faith.
Especially in Theology opposed to agenda, things to be done, matters of practice.
Early 17th century; earliest use found in William Barlow. From classical Latin crēdenda things to be believed, neuter plural of crēdendus, gerundive of crēdere to believe.