"Perfidia (what does that one mean?)"  I guess in our context Perfidia must be a tune by the Glenn Miller Orchestra about some sort of betrayal.   Here is the definitive word by my old buddy John.

By John W. Stewart, 9/19/2002

It is an old Latin word and also an Italian word.

Translated into English, it is: perfidy.

Here you go:

perfidy \PUR-fuh-dee\, noun:
The act of violating faith or allegiance; violation of a promise or vow; faithlessness; treachery.

Soon Esther has fallen desolately into the arms of her girlfriend, seeking advice and reassurance about the perfidy of men.
--Janet Maslin, "Rendezvous in Paris," New York Times, August 9, 1996

Having just fought a war to get rid of a king, the framers had "the perfidy of the chief magistrate" clearly in their sights when they included broad grounds for impeachment.
--Ann H. Coulter, High Crimes and Misdemeanors: The Case Against Bill Clinton

To ordinary Algerians, the news that chemical tests did not end until 1978 was renewed proof of the hypocrisy and perfidy of the military who have misruled them since independence in 1962.
--"Bombshell that rocked generals in Algeria," Irish Times, October 25, 1997

Perfidy comes from Latin perfidia, from perfidus, faithless, treacherous, false, from per-, through (perhaps connoting deviation or infringement, or perhaps explicable by qui per fidem decipit, "who through faith or trust deceives") + fides, faith.