Where does “perfidy” come from?

Perfidy comes from Middle French perfidie, from Latin perfidus meaning faithless, derived from Latin fides meaning faith, ultimately from Proto-Indo-European bʰeydʰ-.

perfidy (English): A state or act of violating faith or allegiance;...

Definitions

  1. A state or act of violating faith or allegiance;...

Ancestry of “perfidy”, step by step

StepLanguageWordMeaning
1Middle Frenchperfidie
2Latinperfidiafaithlessness, dishonesty, treachery, falsehood,...
3LatinperfidusThat breaks his promise; faithless, false,...
4Latinperthrough, by means of; throughout, during
5LatinAdtoward, to
6Latinilliche, she, it, yonder, that, overthere; in that...
7Latinillethat; those; "; demonstrative pronoun "; that...
8LatinolleArchaic form of ille
9Proto-Italic*olnosthat
Every word from Proto-Italic *olnos