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Origin of perfidious

First recorded in 1590–1600, perfidious is from the Latin word perfidiōsus faithless, dishonest. See perfidy, -ous
Related formsper·fid·i·ous·ly, adverbper·fid·i·ous·ness, nounun·per·fid·i·ous, adjectiveun·per·fid·i·ous·ly, adverbun·per·fid·i·ous·ness, noun

Synonyms for perfidious

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Antonyms for perfidious Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for perfidiousness

Contemporary Examples of perfidiousness

  • Third, Munayyer references Plan Dalet as an example of Zionist perfidiousness, a “military plan for the conquest of Palestine.”

    The Daily Beast logo
    (Mis)Interpreting Zionist History

    Brent E. Sasley

    March 19, 2013

Historical Examples of perfidiousness

British Dictionary definitions for perfidiousness


  1. guilty, treacherous, or faithless; deceitful
Derived Formsperfidiously, adverbperfidiousness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for perfidiousness



1590s, from Latin perfidiosus "treacherous," from perfidia (see perfidy). Related: Perfidiously; perfidiousness.

Online Etymology Dictionary, © 2010 Douglas Harper