French leave is "Leave of absence without permission or without announcing one's departure", including leaving a party without bidding farewell to the host. The intent behind this behaviour is to leave without disturbing the host. The phrase was born at a time when the English

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 and French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 cultures were heavily interlinked.

In French, the phrase "filer à l'anglaise" (English leave) means the same thing.

The Oxford English Dictionary records: 'the custom (in the 18th c. prevalent in France and sometimes imitated in England) of going away from a reception, etc. without taking leave of the host or hostess. Hence, jocularly, to take French leave is to go away, or do anything, without permission or notice.' OED states the first recorded usage as: 1771 SMOLLETT Humph. Cl. (1895) 238 'He stole away an Irishman's bride, and took a French leave of me and his master.'

The term is especially used to mean the act of leisurely absence from a military unit. This comes from the rich history of Franco-English conflict

Anglo-French relations

United Kingdom – French relations are the relations between the governments of France and the United Kingdom of Great Britain and Northern Ireland . In recent years the two countries have experienced a very close relationship....

; as Spain

Culture of Spain

The culture of Spain is based on a variety of influences.The Visigothic Kingdom left a sense of a united Christian Hispania that was going to be welded in the Reconquista. Muslim influences were strong during the period of 711 AD to the 15th century, especially linguistically...

 has a similar saying concerning the French (despedirse a la francesa), it may have come from the Napoleonic

Napoleonic Wars

The Napoleonic Wars were a series of wars declared against Napoleon's French Empire by opposing coalitions that ran from 1803 to 1815. As a continuation of the wars sparked by the French Revolution of 1789, they revolutionised European armies and played out on an unprecedented scale, mainly due to...

 campaign

Peninsular War

The Peninsular War was a war between France and the allied powers of Spain, the United Kingdom, and Portugal for control of the Iberian Peninsula during the Napoleonic Wars. The war began when French and Spanish armies crossed Spain and invaded Portugal in 1807. Then, in 1808, France turned on its...

 in the Iberian Peninsula

Iberian Peninsula

The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...

 which pitted the French against an Anglo-Portuguese & Spanish alliance. The phrase has a perfect French and Italian

Italian language

Italian is a Romance language spoken mainly in Europe: Italy, Switzerland, San Marino, Vatican City, by minorities in Malta, Monaco, Croatia, Slovenia, France, Libya, Eritrea, and Somalia, and by immigrant communities in the Americas and Australia...

 equivalent in filer à l'anglaise and filarsela all'inglese, literally, "to take the English leave".

The actual derivation may have its roots in American history during the French and Indian wars. About 140 French soldiers were captured near Lake George

Lake George (New York)

Lake George, nicknamed the Queen of American Lakes, is a long, narrow oligotrophic lake draining northwards into Lake Champlain and the St. Lawrence River Drainage basin located at the southeast base of the Adirondack Mountains in northern New York, U.S.A.. It lies within the upper region of the...

 in New York

New York

New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 and ferried to an island in the lake. The French, knowing the area better than the British, waited until near dawn and quietly waded ashore leaving their captors bewildered on arising. Though its role as such didn't last a day, the island has been named Prison Island.

In Treasure Island, by Robert Louis Stevenson

Robert Louis Stevenson

Robert Louis Balfour Stevenson was a Scottish novelist, poet, essayist and travel writer. His best-known books include Treasure Island, Kidnapped, and Strange Case of Dr Jekyll and Mr Hyde....

, the main character, Jim, refers to taking "a French leave" when he leaves the shelter unbeknownst to the captain.

In the movie Mr. Smith Goes to Washington

Mr. Smith Goes to Washington

Mr. Smith Goes to Washington is a 1939 American drama film starring Jean Arthur and James Stewart about one man's effect on American politics. It was directed by Frank Capra and written by Sidney Buchman, based on Lewis R. Foster's unpublished story. Mr...

Senator Smith is accused of taking "French leave" when he fails to show up at his office in a timely manner upon first arriving in Washington, D.C.