The expression Gallic shrug, also French shrug, denotes a gesture made by a French person to deny responsibility, knowledge or agreement.

Both the expressions French shrug and Gallic shrug occurred, for example, in We’re all right Jacques . . . enjoying life on the sidelines, published in The Birmingham Post (Birmingham, West Midlands, England) of Monday 21^st September 1992:
—Context: A referendum on the Maastricht Treaty (i.e., the Treaty on European Union) was held in France on Sunday 20^th September 1992; it was approved by only 51% of the voters:

Will we meet a French shrug with a stiff upper lip? DENNIS ELLAM takes the pulse of the man in the British street.
True to all the predictions about a nation in confusion, the French have delivered their verdict on Maastricht: neither a No, nor a wholehearted Yes, rather a Gallic shrug.

The Gallic, or French, shrug consists typically in shrugging one’s shoulders while upturning one’s hands—as described in the following two texts:

1-: From Humorous London, published in the Preston Herald (Preston, Lancashire, England) of Saturday 12^th December 1903:

Those hon. members and noble lords who have been invading France are home again full of enthusiasm. They can scarcely be induced to talk English, and several of them have been so Frenchified that they have tried to pass francs as shillings with cabmen. The language of cabby has speedily reminded the forgetful senators that they are in old England once more. Lord Brassey has summed up the situation very nicely for self and friends in the remark, “We have been extremely touched. Our entente cordiale is a great and beautiful idea.” I can imagine the other gentlemen joining in “and so say all of us, which nobody can deny.” I have seen a few of them, and have been much impressed by the big loose neckties they have affected, and the ferocious manner in which they have waxed their moustaches. To see some of them attempt a French shrug, spreading out the palms of their hands on a level with the shoulders is a joy for ever. But the season of fogs and solid pudding and roast beef is setting in, the worthy gentlemen will soon be “quite English, you know,” once more.

2-: From the column Fun and Fancy, published in The Mid-Sussex Times (Haywards Heath, Sussex, England) of Tuesday 13^th June 1905:

A Frenchman, newly imported, attended a Burns celebration in the North. At the end of the jollification a friend asked him if he had enjoyed himself. “Why,” said he, with the characteristic French shrug and upturned hands, “it was magnificent. The haggis was goot, the whisky was very goot, the singing was goot, but who was Mr. Aul Langsyne? Vas he a Scottish chief?”

The earliest occurrences of the expression French shrug that I have found are as follows, in chronological order:

1-: From The Vision of Purgatory, Anno 1680. In which the Errors and Practices of the Church and Court of Rome are Discover’d: With the Influences they have upon This and Other Nations (London: Printed by T. N. for Henry Brome, 1680), by ‘Heraclito Democritus’, i.e., Edward Pettit:

The Capuchin and I were so busie in discourse, that we did not regard three or four modish fellows dancing and curvetting about us, as if the heat of the ground had taught them their Honors, as Banks did his Mare; until one of them interrupted us by desiring to look on the Covenant, which the Capuchin held in his hand: As soon as he had it, he turned to his Companions; and look ye here, cries he, this is A-la-mode de France; ’tis mightily Embarasse, cries a second. Are not these English men, Father, said I? I had no sooner askt the question, but he that had the Scrole in his hand, threw it down, and in the greatest Passion imaginable, English, cries he! I hate the very name, I had rather have a French Disease than English Health. Then lifting up his eyes, Hencefoward [sic] the Fates and I are eternal foes for destining my birth in so unmannerly a Climate: Why was not I a F. Dog, rather than an English man? who (continues he) talks of nothing but old fashioned Honor, Virtue, and Renown; the French alone are the gay and gentile People of the Age, and to whom alone the World is so much indebted for that great Charter of liberty granted the Senses. I am so angry with my Country, cries a second, that I spent my English Estate in France, and was resolved not to enjoy any thing in England, but what I could get by force: For my part, cry’d the third, there is nothing so much troubles me as their Laws, which were they put in execution, there would be no living for men of our quality among them.
At this I askt the Capuchin what they were, who told me that they were Highwaymen, Hectors, and Ranters.
These are a sort of people, whom the Jesuits by their excellent Morals, have made as fit for their purposes, as the other were by their furious and pecipitated [sic] Zeal; whilst they are in the height of their Debaucheries they are utterly disabled from doing any publique good or service; for the little stratagems of Wenching and Drinking are more considerable with them than all real Worth and Generosity; and they think a French Shrug, or a modish Oath the very perfection of Human Nature.

2-: From Popery not Founded on Scripture: Or, the Texts which Papists cite out of the Bible, for the Proof of the Points of their Religion, examin’d, and shew’d to be alledged without Ground (London: Printed for Richard Chiswell, 1688), by the Church of England clergyman Thomas Tenison (1636-1715):

A French Shrug, or an Italian Grimase may be intelligible enough to a Man that understands not one word either of French or Italian; and so may the Cringings, and Bowings, and Prostrations of a Mass-Priest be to the People, tho they understand not one word of all the Latin Service he recites to them.

3-: From The Gentleman Instructed in the Way of Conversation, Entertainment of Friends, Management of his Estate, Company-Keeping, Travelling, &c. (London: Printed for E. Smith, and are to be sold by Richard Wilkin, 1712), by William Darrell (1651-1721):

No doubt (reply’d Eusebius) there are fine things beyond Sea, and a young Man may waft over a handsome Cargo of Italian Improvements, with a Valize of French Behaviour. But, alas, Sir, they will lie upon his Hands, and rust in his Wardrobe for want of using. We hate the stiff and gumm’d Deportment of the Italian, and to be yoak’d in Ceremony or tied up to Steps in Conversation. And the French Shrug only fits tolerably on a Beau, and intitles him to the Honour of a Fop.

The earliest occurrences of the expression Gallic shrug that I have found are as follows, in chronological order:

1-: From a correspondence from Vigo, Spain, dated Sunday 3^rd May 1761, giving the account of the capture, on Saturday 4^th April 1761, of a British ship, the Speedwell, by the French ship Achilles—correspondence published in The Ipswich Journal (Ipswich, Suffolk, England) of Saturday 27^th June 1761:

The French Captain […] permitted an Officer to go on board for their Cloaths, &c. who on his Return to the Speedwell, found her great Cabin almost full of Water, the French Carpenters busy in stopping it, and with some Difficulty got to the Place where his Chest lay; but they had broke it open, and despoiled it of the Contents, leaving nothing but two Trunks of the Captain’s, which they had not been able to get at, and a few Books that lay upon the Cabin-Table, among which was Lord Orrery’s Translation of Pliny’s Letters, which were begged to be returned, as the greatest Favour, because they belonged to the English Consul at Oporto, but a French Officer shook his Head, and with a true Gallic Shrug, told the English Officer he was sorry he could not have the Honour to oblige him.

2-: From The life of George Washington; with curious anecdotes, equally honorable to himself, and exemplary to his young countrymen (Philadelphia: Printed for the author, by R. Cochran, 1808), by Mason Locke Weems (1759-1825):

Soon as it was known by the British Ambassador at Paris, Lord Stormont, that the king of France had taken part with the Americans, he waited on the French minister, De Vergennes *, and with great agitation mentioned the report, asking if it was possible it could be true.
“Very possible, my Lord,” replied the smooth Frenchman.
“Well, I’m astonished at it, sir,” continued Stormont, “exceedingly astonished. America, sir, is our daughter! and it was extremely indelicate of the French king thus to decoy her from our embraces and make a whore of her!”
“Why as to that matter, my Lord,” quoth Virgennes [sic] with the true Gallic shrug, “there is no great harm done. For the king of France is very willing to marry your daughter and make an honest woman of her.”

* Charles Gravier (1719-1787), Comte de Vergennes, was the French Foreign Minister during the War of American Independence (1775-1783); he fashioned the alliance with the North-American colonists that helped them throw off British rule.