A “fait accompli” is an irreversible action that has happened before those affected by it know of its existence and even once the change is found out, the change cannot be undone. In other words, it’s a done deal.
One might think that the expression “fait accompli” jumped from France to England centuries ago during one of the many royal marriages or battles but it would seem that the jump had nothing to do with France at all.
In “The History of Lloyd’s and of Marine Insurance in Great Britain” by Frederick Martin, author of the “Statesman’s Yearbook” and published in 1876, the following passage is found on page 120:
This notice is continued till October 2, 1770, after which it appears slightly varied. Instead of “have been so kind to promise to continue the Ship News,” the alteration, which evidently refers to a fait accompli, appearing for the first time on the 5th of October, 1770.
But 31 years earlier, in 1845, Richard Ford published “A Handbook For Travellers in Spain” which, to this day, is considered to be a classic of travel writing. Ford wrote: “This is now a fait accompli.”
The use of the phrase “fait accompli” in its current sense was used in this way in French as far back as 1222. The Société d’histoire de la Suisse Romande has in its possession a document that states:
Le partage de ses seigneuries entre ses fils laïques, fait par Ebal (IV) de Grandson, était ainsi un fait accompli dans l’année 1222, du moins quant à ses deux fils aînés, puisque nous venons de voir Henri, sire de Champbent, prêter présence lors de l’hommage de Richard de Belmont.
Translated this reads:
The division of his seigniories by Ebal (IV) of Grandson between his sons, was thus a fait accompli in the year 1222, at least with regards to his two oldest sons, as observed by Henri, Lord de Champbent lending his presence to pay homage to Richard de Belmont.
Historically Speaking 