Of American-English origin, the phrases shotgun wedding and shotgun marriage denote a wedding into which one or both partners are forced, usually because the woman is pregnant.

Those phrases originated in the fact that, on occasions, men were actually coerced at gunpoint into marriage, as exemplified by the following from The Cincinnati Enquirer (Cincinnati, Ohio) of Monday 15^th April 1872:

PISTOL PERSUASION.
A Man Married Against His Will Sues for Divorce.
[From the St. Louis Times.]

A novel suit for dissolution of the marriage tie was filed yesterday on behalf of William Fowble vs. Mary Olhausen. The petitioner alleges that on the 8^th of April last, at six o’clock in the morning, the marriage ceremony was performed between him and defendant at the house of William Olhausen, said ceremony being forced on him by the aid and procurement of certain evil-disposed persons, and conducted by Rev. Walker D. Shumate, who certified to the marriage against the will and consent of plaintiff. He further declares that the whole proceedings were false and fraudulent, and then relates the facts in the case as follows: “On the day in question, at five in the morning, William Terry, uncle of defendant, and William Olhausen, her father, presented themselves at the door of his sleeping apartment, in the house of one Eaches, a farmer, by whom he was employed, and then and there compelled him, by threats of death by shooting, to proceed to the house of Olhausen, about half a mile distant, and marry defendant. In consequence of these threats, plaintiff got up, dressed himself, and went to Olhausen’s house, where he remained half an hour—long enough for the performance of the ceremony, which, in spite of protests, entreaties, and tears, was forced on him at the muzzle’s mouth. He alleges, however, that he consistently refused to use the words of assent in the ceremony, constantly declaring that it was no act of his. Plaintiff further alleges that he left the house immediately after the conclusion of the mock ceremony, and has never visited, and will never visit defendant again; and, finally, that the marriage never has been, and never shall be, consummated; he therefore pleads for a release from the unwelcome bonds thus imposed on him by a judicial declaration of invalidity.”

A similar story appeared in The Telegraph and Messenger (Macon, Georgia) of Tuesday 21^st August 1883:

A Shotgun Wedding.
Marshall (Texas) Special.

A very unique wedding occurred in the northern portion of this county this week. It seems that George W. Maynor, a prosperous and respectable farmer, suspected Dr. F. F. Roberts, a nephew of ex-Governor Roberts, of having seduced his eldest daughter, Nottie. Mr. Maynor thereupon procured a marriage license, and with pistols and shotguns, he and his brother, Joseph Maynor, and two other relatives, Thompson and Kelly, arrested Dr. Roberts and forcibly detained him at Mr. Maynor’s residence until a justice could be obtained, when the Doctor was compelled to marry Miss Maynor. Dr. Roberts then left the premises, and has not since returned to Mr. Maynor’s, and says he does not intend to do so. The event has created considerable excitement in Woodlawn neighborhood, and the general impression is that the end is not yet, as the parties are all said to be game, and soar in the first circles.

The earliest instance of the phrase that I have found is cryptic; it appeared in the miscellaneous one-sentence advertisements and pieces of news published in The Globe. A Daily Evening Poster Devoted to Gab and Gossip, and Paid Locals (Atchison, Kansas) of Wednesday 25^th September 1878:

Thompson for hats.
Ash & Payne—visit them.
Gents’ fine hose at Stetter’s.
Sauer Kraut cutters at Harwi’s.
A shot gun wedding is probable.
Boys’ and children’s hats at Stetter’s.
Saratoga dressing—L. K. Wells & Co.
John Dillon will be here October 7^th.
[&c.]

The second-earliest occurrence of the phrase that I have found is in the extended form double-barrel shot gun marriage; it is from one of the unconnected paragraphs published on Wednesday 12^th February 1879 on the last page of the same newspaper, The Globe. A Daily Evening Poster Devoted to Gab and Gossip, and Paid Locals (Atchison, Kansas):

That young man on the north side needs to circumscribe his tender-regard disposition, or there may be a double-barrel shot gun marriage.

The following shocking story was published in The Huntington Democrat (Huntington, Indiana) of Thursday 27^th February 1879:

For general cussedness and low-down brutality, the following, taken from the Marion Democrat, beats anything yet heard of. It says: “Our people will remember that some time since one Robert Kahlo was married to a girl named Kate Moore, living in the south part of town. The marriage was of that kind familiarly called a ‘shotgun wedding.’ Some six months after their marriage a child was born, of which Kahlo declared he was not the father, and gave his wife to understand that she must get rid of it; that if she allowed it to nurse or kept it about the house he would not live with her. The woman, it is said, obeyed orders, and refused the child sustenance until it became so weak from starvation that it was unable to cry even. The neighbors by some means became aware of what was going on, and Esq. Scott, John Harper and others gave them to understand that if they did not stop their fiendish conduct they would be prosecuted. In the meantime Mrs. Ben Page offered to take the infant and care for it. The child was given to her, and it is said to not only have been at the point of death from starvation, but to have been a perfect little mass of filth, its inhuman mother not even having had the decency to wash it. Mrs. Page kept the child for some time, but being a very poor man, Mr. Page finally concluded that he did not feel able to carry this additional burden, and the child was returned to its parents. Shortly after this the Kahlo’s moved into another house, when the beautiful Robert informed his honey of a wife that she must leave the child behind. She did so, and sometime afterward neighbors going into the vacated house found the poor, deserted little waif lying in the wood-box. This raised a regular storm of indignation, and the matter coming to the ears of Mrs. Kahlo’s mother or grandmother, a poor old woman scarcely able to keep herself from want, she agreed to see that the child was cared for if the people would consent not to prosecute them, and thus the matter stands at present. We have given the particulars of this affair just as we got them from the neighbors, and if our statements are correct, we would like to see a coat of tar and feathers applied to this delightful pair, after which they should be ridden on a rail to the river and then baptized until they learn that such heathenish conduct will not be tolerated in a civilized community.”

Those phrases came to also denote any forced union. The following article from the Editorial Page of the San Francisco Examiner (San Francisco, California) of Friday 1^st March 1929 illustrates the transition to this generic sense:

THE SHOTGUN WEDDING

Rev. Kellogg: “Will you take this woman?”
Washington Senate: “Maybe, maybe not – If you’re serious.”
Rev. Kellogg: “Wal, I pronounce you nearly man and wife.”

MARRIAGE A LA MODE.

Pacifists and other simpletons who think the Kellogg pact¹ is a real move to end war should study this cartoon from the London Standard. Better than pages of explanation, it shows us ourselves as others see us.
It depicts the United States reluctantly agreeing to live with the pact—until the day comes to live without it.
The British artist calls it marriage a la mode, which may be translated into plain American as the shotgun wedding.
In shotgun weddings, the bridegroom goes to the altar to save appearances. Nobody with a grain of sense expects the marriage to take.
That is precisely what has happened and will happen again with the Kellogg pact. Its friends and relatives told the Senate, “you ain’t doin’ right by our little girl. You’ll have to make an honest woman of her.” The Senate kept the little gal waiting six weeks at the church before it walked down the aisle with her to the strains of Organist Borah²’s wedding march. And then, by “interpreting” its promise to love, honor and cherish her, it made the ceremony a farce.
As Mr. Glass³ of Virginia aptly said, “it is not worth a postage stamp in the direction of accomplishing permanent international peace.”
The British know it, as the cartoon clearly shows. So do the French, Germans, Italians, Russians and Japanese. So do the Afghans, Albanians, Ethiopians, Icelanders and the forty-nine other peoples invited to attend the function.
Sensible Americans, who have voted by overwhelming majorities against foreign entanglements, know it too.
This is fortunate. Only a few sentimentalists will be surprised when our shotgun bride becomes a grass widow.

¹ The Kellogg Pact, or Kellogg–Briand Pact, also Pact of Paris, was a treaty renouncing war as an instrument of national policy, signed in Paris on 27^th August 1928. It grew out of a proposal made by the French Foreign Minister Aristide Briand (1862-1932) to Frank B. Kellogg (1856-1937), U.S. Secretary of State.

² William Edgar Borah (1865-1940), Senator from Idaho, was a prime advocate of the Kellogg Pact.

³ Although he voted for the Kellogg Pact, Carter Glass (1858-1946), Senator from Virginia, explained: “I am not willing that anybody in Virginia shall think that I am simple enough to suppose that it is worth a postage stamp in the direction of accomplishing permanent international peace”.

Those phrases are also used in the specific sense of: a merger between two companies which takes place in a hurry, usually because one or both of the companies are having difficulties. The earliest occurrences that I have found date from Sunday 2^nd February 1930. That day, the Salt Lake Telegram (Salt Lake City, Utah) published the following:

Morgan Did Not Compel Merger, Behn Declares
Denies I. T. & T. Hookup With R. C. A. Forced by Financier.

Washington, Feb, 1 (UP)—Sosthenes Behn, president of the International Telephone & Telegraph company, denied today that J. P. Morgan & Co. had dictated terms of the contract under which the I. T. & T. had agreed to buy communication facilities of the Radio Corporation of America, provided the government consents.
Appearing before the senate interstate commerce committee, Behn denied intimations by Senator Wheeler, Democrat, Montana, that the proposed merger is to be a “shotgun wedding” with the Morgan company holding the gun.
He asserted that he was the moving spirit in the bargain and had agreed to the price demanded by Owen D. Young of the Radio corporation, even though he believed the price was a “little stiff.”

On the same day, in its account of the same story, the Daily News (New York City, N.Y.) used both shotgun wedding and shotgun marriage.

—Cf. also to ride shotgun.