duplicity

First recorded in 1400–50; late Middle English duplicite, from Middle French duplicitė́, from Late Latin duplicitāt-, stem of duplicitās “doubleness”; see origin at duplex, -ity

1. Duplicity, deceit, guile, hypocrisy, fraud, trickery refer either to practices designed to mislead or to the qualities that produce those practices. Duplicity is the form of deceitfulness that leads one to give two impressions, either or both of which may be false: the duplicity of a spy working for two governments. Deceit is the quality that prompts intentional concealment or perversion of truth for the purpose of misleading: honest and without deceit. The quality of guile leads to craftiness in the use of deceit: using guile and trickery to attain one's ends. Hypocrisy is the pretense of possessing qualities of sincerity, goodness, devotion, etc.: It was sheer hypocrisy for him to go to church. Fraud refers usually to the practice of subtle deceit or duplicity by which one may derive benefit at another's expense: an advertiser convicted of fraud. Trickery is the quality that leads to the use of tricks and habitual deception: notorious for his trickery in business deals.

By and large, the most common sense of duplicity today is “deceitfulness.” The roots of this meaning can be found in the initial “dupl-,” from the Latin duplex, meaning twofold, or double. One can easily see how acting in double, or in two ways at different times, can be a way of deceiving or lying. The duplicitousness of our nature is evident in the widespread usage of other terms with similar roots. Should English speakers be concerned about how the popularity of such terms as “double-dealing,” “double-faced,” and “two-faced” negatively reflect upon our society? Indubitably.

—“The Duplicity of Hargraves”: A short story by O. Henry, first published in 1902.
— Duplicity: A 2009 spy flick starring Julia Roberts and Clive Owen.