The phrase "marriage lines" is listed in the entry for marriage in the Oxford English Dictionary Online (paid subscription required). The phrase is characterized as a colloquial term for a marriage certificate, expecially that held by a bride. The first documented use of this phrase in print was in The Times on 25 March 1818.
As "marriage lines" is considered a colloquialism, it is not surprising that it is not found in written or printed form until 1818. In fact, it is a mark of its pervasiveness in the language by this time that it did find its way into print. A colloquialism is, by definition, an expression which is not typically used in formal speech or writing. But it is a common part of informal speech, the daily conversation of regular people. So, it is clear that "marriage lines" was used in daily speech by ordinary people for many years before its first appearance in The Times in 1818.
"Marriage lines" is also an idiom, as it seems quite clear it is peculiar to the English speakers of the British Isles. There is no evidence this phrase was commonly used by the populations of any of the countries of the European Continent, or even in America or Canada, except by native British speakers.
So what is the origin of this charming expression for a marriage certificate? And why were the "marriage lines" so important to the women who possessed them?
I believe that the use of the term "marriage lines" began in England shortly after the passage of the English Marriage Act of 1753, also known as Lord Hardwicke’s Marriage Act, after the man who shepherded it through Parliament. I recently had occasion to read the full text of the Marriage Act and discovered that there was a clause in it which explicitly calls out how each marriage is to be recorded, right down to the ruled lines in the record books. That clause is quoted in full below:
XIV. And for preventing undue entries and abuses in registers of marriages; be it enacted by the authority aforesaid, That on or before the twenty-fifth day of March in the year one thousand seven hundred and fifty-four, and from time to time afterwards as there shall be occasion, the church-wardens and chapel-wardens of every parish or chapelry shall provide proper books of vellum, or good and durable paper, in which all marriages and banns of marriage respectively, there published or solemnized, shall be registered, and every page thereof shall be marked at the top, with the figure of the number of every such page, beginning at the second leaf with number one; and every leaf or page so numbered, shall be ruled with lines at proper and equal distances from each other, or as near as may be; and all banns and marriages published or celebrated in any church or chapel, or within any such parish or chapelry, shall be respectively entered, registered, printed, or written upon or as near as conveniently may be to such ruled lines, and shall be signed by the parson, vicar, minister or curate, or by some other person in his presence, and by his direction; and such entries shall be made as aforesaid, on or near such lines in successive order, where the paper is not damaged or decayed, by accident or length of time, until a new book shall be thought proper or necessary to be provided for the same purposes, and then the directions aforesaid shall be observed in every such new book; and all books provided as aforesaid shall be deemed to belong to every such parish or chapelry respectively, and shall be carefully kept and preserved for publick use.
The next clause in the Marriage Act calls out exactly how the registration of each marriage is to be recorded by the officiating clergyman on these "lines" in the parish "register" book. It included an example of the exact format for the registration record, which I have replicated below the full text of this clause.
XV. And in order to preserve the evidence of marriages, and to make the proof thereof more certain and easy, and for the direction of ministers in the celebration of marriages and registering thereof, be it enacted, That from and after the twenty-fifth day of March in the year one thousand seven hundred and fifty-four, all marriages shall be solemnized in the presence of two ore more credible witnesses, besides the minister who shall celebrate the same; and that immediately after the celebration of every marriage, an entry thereof shall be made in such register to be kept as aforesaid; in which entry or register it shall be expressed, That the said marriage was celebrated by banns or licence; and if both or either of the parties married by licence, be under age, with consent of the parents or guardians, as the case shall be; and shall be signed by the minister with his proper addition, and also by the parties married, and attested by such two witnesses; which entry shall be made in the form or to the effect following; that is to say,
I think it is clear after reading these two clauses of the Marriage Act how the phrase "marriage lines" made its way into the colloquial speech in England during the mid-eighteenth century. After each marriage ceremony, the officiating clergyman, the newly married couple and their witnesses would retire to the vestry of the church, where the minister would record the marriage as prescribed by the Marriage Act on the "lines" ruled in the registry book kept for the purpose, and all parties would sign it.
This same record of the marriage would then be copied out onto a separate sheet of paper, also signed by all of those who participated in the ceremony. According to tradition, this document was handed to the best man, who in turn gave it into the keeping of the new bride. In some cases, the presiding clergyman gave it directly to the newly married lady, but it was never given to the groom. This certificate of the marriage was considered the property of the bride.
Why were these "marriage lines," the certificate of her marriage, given to the bride, not the groom, by law her new lord and master? Because proof of her married state was much more important to a woman than to a man. Particularly among those of the lower classes, a woman’s social standing, in some cases her very survival, depended upon her ability to prove she was a respectable married woman. A man could live anywhere he chose, with anyone he chose, and little would be said. But a woman who was thought to be living with a man without benefit of clergy could be exposed to any number of dangers. She could not depend on her husband for support if she could not prove she was his legal wife, she would be exposed to taunts and insults, she might even be liable to arrest and incarceration as a prostitute. If she was a widow, she could be denied her lawful dower rights, even custody of her own children. As you might imagine, most women would safeguard their "marriage lines" above all their possessions.
Some women also kept their "marriage lines," safe for sentimental reasons. They loved their husbands, were happy in their marriages, and therefore this certificate was precious to them as a symbol of that love and happiness. In addition, many women were superstitious about the success of their marriage if anything should happen to the "original" certificate. From the mid-eighteenth century well into the nineteenth century, it was a rather complicated process to get a copy of a marriage certificate. And, it would only be a copy, if the original was lost. For these reasons this treasured document was cherished.
Now, the next time you come across the phrase "marriage lines" in a Regency novel you will understand the path it took into the language of the time. You will also know that those authors using "marriage lines" who set their novels in the Medieval, Tudor or Stuart eras have not done their homework, as this phrase did not enter into the language of England until the mid-Georgian period and did not enter into print until the late Regency.
And you will know why any woman in possession of such a document kept it safe, and usually close, throughout her life. It was proof of her legal status as a respectable married woman, with all of the attendant perquisites. A man’s marital status had far less impact on his prosperity or his social standing in the community, so he had less need to have custody of this document. But for many women, her "marriage lines" were proof of one of the most important achievements of her life, and might be her best protection against life’s vicissitudes.