In the USA, cocked hat denoted a game similar to ninepins, except that only three pins were set up, in triangular position. It took its name from cocked hat in the sense of a hat with the brim permanently turned up (i.e. cocked), especially the three-cornered hat of this shape worn at the end of the 18^th and beginning of the 19^th century. The Daily Northwestern (Oshkosh, Wisconsin) of 21^st November 1900 evoked the game:

Bowling has taken hold of Oshkosh with a vengeance and the sport becomes more and more fascinating to those who enjoy the exercise and excitement of rolling the ball down the highly polished alley, scattering the pins right and left for a “strike” or “spare,” if the game is cocked hat or ten pins. While ten pins is played on a number of the leading alleys, it is by no means the most popular game, for the more difficult game of “cocked hat,” or three pins, is the most in favor with the veteran players, who are experts. With the beginners and the players who play but rarely, ten pins is the common game, as the scores come easier and the man who is able to roll the ball on the narrow alley at all is quite sure of getting some sort of a score.

The phrase to knock into a cocked hat, of American origin, means to outdo or defeat, to damage or spoil completely. It is often said that it implies a comparison between the disorder ensuing a defeat and the way in which the pins are bowled down at the game of cocked hat. An alternative origin was suggested in The St. James’s Gazette (London) of 24^th March 1902:

Knocked into a Cocked Hat.

The expression “knocked into a cocked hat,” is familiar to everyone, but perhaps its origin is not so generally known. Cocked-hat was a variety of the game of bowls, in which only three pins were used, set up at the angles of a triangle. When, in bowling ten pins, all were knocked down, except the three at the corners, the set was said to be “knocked into a cocked-hat,” whence the popular expression for depriving anything of its main body, character, or purpose.

But these two explanations are likely to be later rationalisations, as the early instances of the phrase show no connexion with the game of cocked hat. The image is more probably either the appearance of something, or of a face, that has been altered by being knocked, or a person’s head being forced to fit into a cocked hat, as the American novelist William Alexander Caruthers (1802-46) seems to indicate in The Kentuckian in New-York. Or, the adventures of three Southerns. By a Virginian (New York, 1834); Montgomery Damon, the Kentuckian, is at an opera performance:

We found great difficulty in getting Damon to understand, with his shrewd natural view of things, that an opera was nothing more than a common play; the parts being sung, instead of spoken.
“Now I wish my head may be knocked into a cocked-hat, if a man had told this to me of the Yorkers in old Kentuck, if I wouldn’t have thought he was spinnin long yarns; there is no sense in it.”

The earliest instance of the phrase that I have found is from the Frederick-Town Herald (Frederick, Maryland) of 13^th November 1830:

Come just wet your whistle again, ’fore we’re off, its free as water to him what’s the friend of Henry Clay. Tho’ I’ll tell ye what, stranger, I’m none your mealy mouthed fellows, and I’m little jubus [= dubious] that you’re one of them there Adams men. And I’ve just seen the time that I’d knock sich a fellow into a cocked hat as quick as name it. But Jackson is safe enough and he’s jist the chickin what’s able; Adams is done for til he’s made over.

The author of a portrait of ‘Aminadab Halfanhouraftereverything’, published the North Carolina Spectator and Western Advertiser (Rutherfordton, North Carolina) of 1^st October 1830, punned on the phrase:

His dress consists of a hat with “no rim nor nothing, “knocked into a cocked hat” by hard usage, and covered with various kinds of grass-seed, chalk, white-wash, cob-webs and stable litter.

The following is from The Boston Morning Post (Boston, Massachusetts) of 27^th June 1833:

A N. York paper giving the details of a riot which occurred in that city, says that “a person was struck with a brick-bat, and knocked into a wheel-barrow.” We have before heard of persons being “knocked into a grease spot*,” and of others who had been threatened with being “knocked into a cocked hat,” but this is the first time we ever heard of any one being “knocked into a wheel-barrow.”

(* In The Slang Dictionary (London, 1865), the English author and publisher John Camden Hotten (1832-73) defined grease-spot as “a minute remnant, the only distinguishable remains of an antagonist after a terrific contest”.)