Perfidious

Perfidious (pronounced per-fid-e-us)

Deliberately faithless; treacherous; deceitful.

1590-1600: From the Latin perfidiōsus (faithless, dishonest, treacherous), the construct being perfidia + -ōsus.  The source of perfidia was perfidus (faithless), the construct being per (through) + fidēs (trust), from the primitive Indo-European per + the Proto-Italic feiðos from the root bheydh.  The English suffix –ious (full of, overly, prone to), used to form adjectives from nouns, was from the Latin –ōsus, from the Proto-Italic -owonssos from -o-wont-to-s, the last form a combination of two primitive Indo-European suffixes, (1) -went- (also -wont-) and (2) -to-.  The Latin was related to the Ancient Greek -εις (-eis).  Perfidious is an adjective, perfidiously is an adverb and perfidiousness is a noun; the noun plural is perfidiousnesses.

UK prime-minister Anthony Eden (1897-1977; UK prime-minister 1955-1957, later Lord Avon) with his French counterpart, Guy Mollet (1905–1975; French prime-minister 1956-1957), March 1956.

Used memorably in the phrase perfidious Albion (Albion is a poetic name for Britain), the adjective perfidious is an Anglophobic pejorative phrase used in histories of international relations to refer to diplomatic slights or acts of treachery and infidelity by the British (and especially the English).  There being many from which to choose, complaints about British foreign policy have not been without foundation but duplicity is the lingua franca of diplomacy and the UK Foreign Office probably tended just to be better at it than many.  In the Foreign Office, a word like "faithless" is thought "charming but not a great deal of help" and if they're thought manipulative or duplicitous in their dealings with others, it's because that's just the way business is done.  It's not known if terms like "faithless" or "perfidious Albion" were on Lindsay Lohan's mind while she was tweeting in support of the #remain cause on the day of the Brexit referendum. 

Although the sentiment exists in documents from the thirteenth century, origin of the phrase in its current form, is usually attributed to Augustin Louis de Ximénès (1728-1817), a French playwright who included the line "Attaquons dans ses eaux la perfide Albion" (Let us attack perfidious Albion in her waters) in his poem L'Ère des Français (1793), written at the start of the French Revolutionary wars.  In the Second Reich, das perfide Albion became frequently used especially during the reign of Kaiser Wilhelm II (1859–1941; German Emperor & King of Prussia 1888-1918) and later the Duce (Benito Mussolini (1883-1945; Duce (leader) & prime-minister of Italy 1922-1943) liked it; Mussolini complaining in his fluent French of perfida Albione whenever British foreign policy didn’t suit, which was often.  Even the English aren’t averse to its use.  Anthony Eden, answering some criticism from the Quai d'Orsay over Britain’s conduct during the 1956 Suez crisis, answered simply “perfidious Albion”.

Before Broken English:  Marianne Faithful, Faithless (1978 NEMS Cat: NEL 6012), repackaged re-release of Dreamin' My Dreams (1976).