Of U.S.-English origin, the noun Briticism denotes a word, expression, grammatical construction, etc., characteristic of or restricted to British English, especially as compared with U.S. English.

This noun was coined by the U.S. literary and musical critic, Shakespearean scholar, journalist, social critic and lawyer Richard Grant White (1822-1885):
– to denote a word or expression whose original acceptation (preserved in U.S. English) was, in British English, changed to one that he regarded as debased;
– in Words and their Uses, first published in instalments in 1868 in The Galaxy. An Illustrated Magazine of Entertaining Reading (New York: Sheldon & Company).

Richard Grant White contrasted British English with U.S. English in the introduction to the chapter titled Some Briticisms. Squeamish slang. “Misused words.”, published in The Galaxy of October 1868:

I have heretofore designated the misuse of certain words as Briticisms. There is a British affectation in the use of other words, which is worthy of some attention. And when I say that a form of speech is of British origin, or is a Briticism, I mean that it has arisen or come into vogue in Great Britain since the beginning of the eighteenth century, when, by the union of England and Scotland (A. D. 1707) the King of England and of Scotland became King of the United Kingdom of Great Britain and Ireland, a British took the place of an English Parliament, and Englishmen became Britons. This period is one of mark in social and literary, as well as in political history. To us it is one of interest, because, about that time, although our political bonds were not severed until three-quarters of a century later, our absolute identity with the English of the mother country may be regarded as having ceased. For, after a moderate Jacobite exodus at the end of the seventeenth century, there was comparatively little emigration from the old England to the new. They change their skies, but not their souls who cross the sea; and whatever the population of this country may become hereafter, it had, till within twenty-five years, remained, as to race, an English people, just as absolutely as if our fathers had remained in the Old Home. The history of England, of the old England, pure and simple, is our history. In British history we have only the interest of kinsmen; and John Bull, whose face, figure, and manners were unknown in England until the eighteenth century, is only our cousin. But he and we possess the English language and English literature before the British period in the same completeness and by the same title—inheritance from our common fathers, who spoke it and wrote it, quickened by the same blood, on the same soil. And, in fact, the English of the period when Shakespeare wrote and the Bible was translated, has been kept in use among people of education more in the new England than in the old. All over the country there are some words and phrases in common use, and, in certain parts of New England and Virginia, there are many which have been dropped in British England, or are to be found only among the squires and farmers in the recesses of the rural counties. The forms of speech which may be conveniently, and, I think, correctly, called Briticisms, are, however, generally of later origin than the beginning of the British Empire. They have almost all of them sprung up since about A. D. 1775.

These are two of the Briticisms that Richard Grant White mentioned in the same issue of The Galaxy:

Sick and Ill are two other words that have been perverted in general British usage. Almost all British speakers and writers limit the meaning of sick to the expression of qualmishness, sickness at the stomach, nausea, and lay the proper burden of the adjective sick upon the adverb ill. They sneer at us for not joining in the robbery and the imposition. I was present once when a British merchant receiving in his own house a Yankee youth at a little party, said, “Good evening! We haven’t seen you for a long while. Have you been seeck” (the sneer prolonged the word), “as you say in your country?” “No, thank you,” said the other, frankly and promptly, “I’ve been hill, as they say in yours.” John Bull, although he blushed to the forehead, had the good sense and the good nature to join in the laugh that followed; but I am inclined to think that he never ran another tilt in that quarter. As to the sense in which sick is used by the best English writers, there can be, of course, no dispute; but I have seen this set down in a British critical journal of high class as an “obsolete sense.” It is not obsolete even in British usage. British officers have sick leave; British invalids keep a sick bed, or a sick room, and so forth, no matter what their ailment. No one of them ever speaks of ill-leave, an ill-room, or an ill-bed. The incongruity is apparent, and it is new-born and needless. For the use of ill—an adverb—as an adjective, thus: an ill man, there is no defence and no excuse, except the contamination of bad example.

Stop for stay is a Briticism. E. g., “stop at ’ome.” To stop is to arrest motion; to stay is to remain where motion is arrested. “I shall stop at the Clarendon,” says our British friend—one of the sort that does not “stop at ’ome.” And he will quite surely stop there, but after he has stopped, whether he stays there, and how long, depend upon circumstances. A railway train stops at many stations, but it stays only at one.

Richard Grant White had already used Briticism in previous instalments of Words and their Uses—for example:

1-: In the chapter titled Oliver Cromwell on the use of words.—Misused words.—Briticisms.—Howells’ “Italian Journeys.”, published in The Galaxy of March 1868:

Directly.—The radical meaning of this word is, in a right line, and hence, as a right line is the shortest distance between two points, it means at once, immediately. Its synonyme [sic] in both senses is a good English word, now, unhappily, somewhat obsolete, straightway—our equivalent of which, right away, is laughed at by brother Bull as an Americanism. But John Bull himself uses directly in a way which is quite insufferable—to wit, in the sense of when, as soon as. This use of the word is a widespread Briticism, and prevails even among the most cultivated writers. For instance, in the London “Spectator” of May 2, 1867, it is said that “Directly Mr. Disraeli finished speaking, Mr. Lowe rose to oppose,” etc. Anglice, As soon as Mr. Disraeli finished speaking, etc. It is difficult to trace by continuous steps the course of this strange perversion, for which there is neither justification nor palliation.

2-: In the chapter titled Misused words. Making pronouns. Pease and pison., published in The Galaxy of August 1868:

Awful.—It would seem superfluous to say to the readers of The Galaxy that awful is not a synonyme [sic] of very, were it not that the word is thus used by many people who should know better than to do so. The misuse is a Briticism; but it has been spreading rapidly here during the last few years. I have heard several educated English gentlemen speak in sober, unconscious good faith, of “awfully nice women,” “awfully pretty girls,” and “awfully jolly people.” That is awful which inspires or is inspired by awe; and in the line in the old metrical version of the Hundredth Psalm,
                         Glad homage pay with awful mirth,
Tate and Brady ¹  did not mean that we were to be awfully jolly or very mirthful or gay in our worship. Observe here again how misuse debases a good and much needed word, and voids it of its meaning; by so much impoverishing the language.

¹ Nahum Tate (1652-1715) and Nicholas Brady (1659-1726) produced a metrical version of the Psalms, titled New Version of the Psalms of David. Fitted to the Tunes Used in Churches (London: Printed by M. Clark for the Company of Stationers, 1696).

Richard Grant White’s approach to language was normative, prescriptive, as opposed to that of the U.S. author and educator Brander Matthews (1852-1929), Professor of Dramatic Literature at Columbia University, who wrote the following in Parts of Speech: Essays on English (New York: Charles Scribner’s Sons, 1901):

For an Englishman to object to an Americanism as such, regardless of its possible propriety or of its probable pertinence, and for an American to object to a Briticism as such—either of these things is equivalent to a refusal to allow the English language to grow. It is to insist that it is good enough now and that it shall not expand in response to future needs. It is to impose on our written speech a fatal rigidity. It is an attempt on the part of pedants so to bind the limbs of the language that a vigorous life will soon be impossible. With all such efforts those who have at heart the real welfare of our tongue will have no sympathy—least of all the strong men of literature who are forever ravenous after new words and old. Victor Hugo ², for example, so far back as 1827, when the modern science of linguistics was still in its swaddling-clothes, had no difficulty in declaring the truth. “The French language,” he wrote in the preface to ‘Cromwell,’ ³ “is not fixed, and it never will be. A living language does not fix itself. Mind is always on the march, or, if you will, in movement, and languages move with it. . . . In vain do our literary Joshuas ⁴ command the language to stand still; neither the language nor the sun stands still any more. The day they do they fix themselves; it will be because they are dying. That is why the French of a certain contemporary school is a dead language.”

² Victor Hugo (1802-1885) was a French poet, novelist and playwright.
³ More famous than the play, Hugo’s Preface to Cromwell (1827) became the manifesto for French romantic drama in its battle against the sclerotic neoclassical rules.
⁴ In the Book of Joshua, 10:12, Joshua, as leader of the Israelites, asks God to cause the moon and the sun to stand still so that he and his army might continue fighting by daylight.