The Latin verb fidere means “to trust.” Adding the prefix con-, “with,” gives confidere, “to have full trust or reliance.” According to a note in the OED, the word may have originated to show the relationship between two people, “two friends who mutually confide in or trust each other, and hence are trusted by each other.” In time, the word came to be used in a more general sense.
The noun confidence has a variety of meanings. As a synonym for faith or trust, it means “the mental attitude of trusting in or relying on a person or thing”:
And we have confidence in the Lord touching you, that ye both do and will do the things which we command you. 2 Thessalonians 3:4, KJV.
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Confidence can mean feeling sure of a fact or an issue:
Climate models now include more cloud and aerosol processes, but there remains low confidence in the representation and quantification of these processes in models.
Speakers frequently use confidence in the sense of “assurance arising from reliance on oneself:
What can I do to help my child have confidence when in new situations?
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Confidentiality is required of lawyers, priests, social workers, and anyone else to whom private matters are confided. For example:
There are many specific areas regarding consent and confidentiality that are particularly difficult for teens, parents, health care professionals and lawmakers.
Other “with trust” words: confident (adjective), confidential (adjective), confidentially (adverb), and confide (verb):
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Teachers should discuss such matters confidentially with individual parents.
Confidentially, I don’t much care for the terms Usonian and Usonia.
It’s difficult nowadays to keep personal information confidential.
It was a mistake to confide in her: she posted everything I told her on Facebook.
Before 1700, a person trusted with private information, “usually amorous,” was called a confident [sic]. Then the French word confidant/confidante entered the language. For a time, English speakers observed the masculine/feminine differences in writing, but now a confidant can be either a man or a woman. Anyone familiar with the television series The Golden Girls is acquainted with the opening words of its theme song:
Thank you for being a friend
Traveled down the road and back again
Your heart is true, you’re a pal and a confidant.
Finally, there’s such a thing as too much confidence, either because a person thinks he knows it all, or because a person trusts the wrong person:
Malcolm Gladwell drew an important distinction between the normal mistakes that result from incompetence (not knowing enough) and mistakes made because of the overconfidence of experts (miscalibration).
San Antonio police have arrested a fugitive accused of running a long-term confidence scheme with victims in Ohio, Florida and Texas. He repeatedly befriended his victims, convinced them to give him thousands of dollars and then absconded with the money.