Double-barrelled names are everywhere. At my state primary in the 1970s, no child had more than one last name. Last week, when England won the under-17 World Cup, two of the starting 11 had two last names, and there were three more double-barrels on the substitutes bench. In the England squad that won the under-20s World Cup in June, there were four more double-barrelled players, including Everton’s Dominic Calvert-Lewin. Then, on Wednesday, the London Mint Office published research by Opinium which found that 11% of people aged between 18 and 34 double-barrelled their surname when they got married.

Even allowing for the fact that football is becoming a more middle-class profession, these numbers suggest that a double-barrelled name no longer denotes the upper tier of society. But double barrels are caught in their own double bind – no longer posh, yet still taken as such. So why are they proliferating – and how should we negotiate their complexity?

“First names are about individuals, but surnames are about your connectedness with other people,” says Jane Pilcher, a professor at Leicester University who specialises in the sociology of names. “Surnames link you with your family, but also with your national heritage, your ethnic heritage.”

When she married, Pilcher retained her surname. Then she had children, and the subject felt complicated. “I didn’t see why my children should have only my husband’s name,” she says. But first she had to overcome a stumbling block. “In English cultures there’s an association of double-barrelled names with being very posh. I had struggled with it.” She reconciled herself by deciding not to join the children’s two surnames with a hyphen. “I wanted it to be a double surname, rather than a double-barrelled surname,” she says.

This sounds like a lot to lay on the smallest line in English punctuation, but hyphenless doubles are increasingly common. Call it the Hillary Rodham Clinton or Kim Kardashian West model. (There are a few hyphenless doubles among those England footballers, too.) However, a hyphen is a shaky foundation on which to build a sociological theory. I am not sure that Pilcher’s distinction between a double name and a double-barrelled name holds, since “double-barrelled” was first used to describe names in the mid-19th century, long after the practice of deploying a double surname became fashionable.

Besides, when it comes to hyphens, some families don’t even align. Sacha Baron Cohen has no hyphen, but his cousin Simon Baron-Cohen does. Helena Bonham Carter has described hers as optional. And even Pilcher says people commonly insert a hyphen between her children’s two last names, thereby barrelling them despite her best intentions.

Equality is clearly one motivator behind the proliferation of the double barrel. “We wanted to celebrate the fact that we were modern people,” says Ben Eden-Davies, who was Ben Davies before he married Camilla Eden. “As a married couple, we wanted to have a collective identity,” which they now share with their daughter.

But there are other reasons for the surge in popularity of two names. The rise of the blended family, for instance, has triggered a sort of familial reorganisation which has required a familial renaming. I know of people who had single barrels until their parents divorced, and they wanted, retrospectively, to hitch themselves in name to both parents. I know of others who lived single-barrelled until the unnamed parent remarried and belatedly doubled. I know of others still who adopt a second barrel in order to preserve their ethnic or social heritage. (I can relate to this. I have opened discussions in my own family to insert my surname into my children’s names as a sort of invisible middle name, a kind of secret pocket they can tap now and then to check their Italian heritage is safe.) There are some – such as Dawn O’Porter (born Dawn Porter) – who blend their name with a partner’s to create a fresh name, or give their children totally invented last names. And others still who decide which name to give on the toss of a coin.

“It’s a practical issue that needs to be resolved, and I don’t know if it is resolvable,” Pilcher says. “I think it depends on how people feel about their children having the same name as themselves.”

So how do you tell a posh one from a non-posh one?

“I’m not sure you can,” she says.

Fashion is clearly a contributory factor here. The rise in the double-barrelled surname has been accompanied by a rise in the double-barrelled first name (raising the possibility of multi-hyphenated future adults). In 2014, almost 1,200 hyphenated first names were registered for baby girls.

And although there are plenty of people, such as Pilcher or Eden-Davies, who worried that a double-barrelled name “could seem quite pretentious”, there are others attracted to the social privilege that still attends double barrels. Two years ago, Debrett’s Foundation released research that found a quarter of Britons aged 16 to 25 believed a double-barrelled name made it easier to get a work placement.

Maybe this is not surprising given that the double surname, initially the preserve of aristocrats, became a micro trend in Tudor England, according to Else Churchill of the Society of Genealogists, with “gentry families trying to emulate the aristocracy because they have bought off dissolved monasteries”. It was in the mid-19th century that two hyphenated last names really became popular, with “doctors, lawyers, people who are gaining status not through genealogy and land-owning title but through professions” emulating the aristocratic habit of double-barrelling.

“It’s a nightmare for genealogists trying to index,” says Churchill. “It can be quite fun. It’s a challenge.” She says she is still trying to find the birth entry of one member of the society who died in the 70s, and who used a surname as a middle name, because, historically, there has been no uniformity in the way that double-barrelled names are entered on the register of births.

Naming children, and re-naming ourselves, is clearly a complicated business. Some countries have negotiated the difficulty through law. In France, two consecutive hyphens were used to distinguish between newly formed double surnames and double names with heritage. Chinese marriage law states that a child may use either parent’s surname, although a survey by the ministry of public security in 2007 found that 85% of Chinese people share 100 surnames. Globalisation and immigration patterns have also caused naming conventions to change, with the traditional chain of Arabic names morphing in some places to resemble a forename/surname pattern.

And even those who engage in a kind of mindful barrelling for the explicit purpose of rendering two parties equal in a marriage have not found a future-proof solution.

Those double-barrelled children, at birth the perfect expression of an equal partnership, will grow up and form relationships of their own. And if they choose to partner, they will have to negotiate their own re-naming. A double-barrelled name built on the grounds of equality differs from a double-barrel built on inheritance in one crucial regard. It cannot be handed down intact. That is because an egalitarian double-barrelled child might easily meet another double-barrelled child. Two barrels coupled make four barrels. Four barrels coupled makes eight barrels. You can see where this would end. (The 5th Earl of Wharnclife is Richard Montagu-Stuart-Wortley-Mackenzie. But even in Burke’s Peerage this is rare.)

As a model for future generations of equal naming, the double barrel contains this inherent fallacy: it is necessarily short-lived, an interim solution, and whatever you call your offspring, they will, on marriage, civil partnership or parenthood, have to answer this question for themselves. There are countless women with double-barrelled names, given to them by feminist parents in the 1960s, 70s and 80s, who have renounced those names on marriage because a double-barrelled name might fix one generation’s problem but not the next’s.

Still, as we embrace greater fluidity in all parts of life, from gender to sexuality, ageing to technology, maybe we shouldn’t worry. As Else Churchill says, “Names have always been fluid.”