Perfidious
/pərˈfɪd.i.əs/noun
Deceitful and untrustworthy, especially in a way that betrays trust.
Did you know?Perfidious comes from Latin perfidiosus, built on per- (“through, beyond”) + fides (“faith, trust”), so its oldest core is the idea of someone who has pushed past faith into treachery.
Etymological Timeline
Proto-Indo-European
PIE
*bheidh-
“to trust, confide, persuade”
Latin
Latin
fides
“faith, trust, loyalty”
Latin
Latin
perfidia
“breach of faith, treachery”
Late Latin
Latin
perfidiosus
“treacherous, faithless”
Middle English
English
perfidious
“deceitful, faithless, treacherous”