Definitions: (1) self-satisfied; self-possessed; bold; (2) convinced of the certainty or truth of a matter; confident; authoritative

Derivation: Latin, “toward security”
Note: The original Latin indicates there is always a bit of uncertainty in most certainties.

Quote: Be assured that if you knew all, you would pardon all. — Thomas à Kempis (1380–1471) Author of The Imitation of Christ