Perfidy

noun

The state or quality of being untrustworthy, dishonest, or disposed to betrayal
An action or incidence of disloyalty or duplicity

Usage

Be careful who you trust - you'll need constant vigilance to stay clear of perfidy! Perfidy is a noun that describes the trait of being untrustworthy or deceitful. It can also refer to a specific situation or act of betrayal. This is one word with some serious implications; anyone who engages in perfidy is likely performing the kind of infidelity that breaks friendships, ruins relationships, and even breaches national security (think Benedict Arnold). The typical use of this term suggests that someone who was once trusted or considered honorable has gone against the faith placed in them, possibly causing significant harm to the other party. Thus, an act of perfidy is considered highly offensive and often unforgiveable. Perfidy is, however, a wonderful word to sneak into conversation - trust us!

Example: : The assassination of Julius Caesar by Brutus and Cassius is one of the most infamous (and occasionally exaggerated) acts of perfidy in history.

Example: The spy spoke so affably that no one ever suspected her of perfidy.

Origin

Don't be deceived by perfidy's seamless fit in the English language - the word is actually Latin in origin. Perfidy's Latin ancestor, perfidia, was formed from the roots per and fides, which, taken together, imply a harm that comes about from having put faith in something. Perfidy had made its way into English conversations by the end of the sixteenth century, and it has been used to describe various nefarious acts ever since.

Derivative Words

Perfidious is an adjective which describes something or someone as being treacherous or untrustworthy; similarly, perfidiousness is a noun which refers to the quality of unfaithfulness or untrustworthiness (making it often interchangeable with perfidy). Finally, perfidiously is an adverb that refers to an action connected to betrayal.

Example: Michelle was shocked to learn of the perfidiousness of her cheating husband.

Example: Over a period of many years, the minister perfidiously embezzled thousands from church donations.

Example: Giving his boss a perfidious smile, Jorge discreetly slipped the poison into the man's glass.

In Literature

From Kate DiCamillo's The Tale of Despereaux: Being the Story of a Mouse, a Princess, Some Soup and a Spool of Thread:

Isn't it ridiculous to think that a mouse could ever forgive anyone for such perfidy?

Here, the author highlights how unusual it is for the main character to forgive an act of treachery.

From Thomas Jefferson's Declaration of Independence:

He is at this time transporting large armies of foreign mercenaries to complete the works of death, desolation, and tyranny already begun with circumstances of cruelty and perfidy scarcely paralleled in the most barbarous ages, and totally unworthy the head of a civilized nation.

Here, Jefferson uses perfidy to describe the King of England as betraying the people he is meant to govern. This went counter to the American Founding Fathers' ideal of a government by and for the people.

Mnemonic

A stab in the back is the perfect example of perfidy.
Perfidy is perfect infidelity