perfidious

the word "perfidious" has a clear and logical construction from its latin components. it originates from the latin perfidia, meaning "faithlessness, treachery", which itself is built from per- (here intensifying to mean "to bad effect, destructively") and fides ("faith, trust"). the literal sense is thus "characterized by a destructive violation of faith". this meaning traveled directly into english in the late 16th century via the french perfide, retaining the strong connotation of a deliberate and wicked betrayal of trust, rather than mere dishonesty. the story of the word is one of a sacred bond (fides) being thoroughly (per-) broken.

Structure: per (through, to destruction) + fid (faith, trust) + ious (adjective suffix) - per: a latin prefix meaning "through, thoroughly, to destruction, badly". - fid: from latin fides, meaning "faith, trust, confidence". - ious: a latin-derived adjective-forming suffix meaning "full of, characterized by".