LONDON – Since the royal engagement of Prince William and Kate Middleton, one word describing the bride-to-be has stood out more than any other. She may be beautiful, graceful and fabulously rich, but Middleton is still a “commoner.”

Technically, the label fits. The 28-year-old daughter of former airline workers made good is not of noble blood and, hence, considered a commoner in the British tradition of class distinction. Yet the wide use of such an archaic and, to some, pejorative term is igniting a heated debate here about pedigree and status in modern Britain.

Royal watchers and the British media are not mincing words about the humble lineage of “Commoner Kate.” “From pit to palace,” declared London’s Daily Mail, noting her great-great-grandfather’s days as a coal miner. “I’m not against the middle class as such, but I do query whether she has the background and breeding to be queen one day,” wrote James Whitaker, a guru of royal gossip. The Guardian, the Times of London, the Telegraph and the venerable BBC, among others, have all seen fit to dub her a “commoner.”

Others here are wincing at the notion that a young woman whose family’s self-made fortune is larger than many in the landed gentry is being so strongly defined by her bloodline in 21st-century Britain. It shows, observers say, that despite the rise of mega-rich commoners such as Richard Branson and J.K. Rowling, this is still very much a society where status is measured in birthright and breeding.

“It’s quite depressing, this word, like we’re going back to a 19th-century theme-park Britain, to an age of deference to the monarchy,” said Evening Standard columnist Richard Godwin, who penned a piece about the term. “But most of all, you look at Kate’s background and you see there is nothing common about her.”

In fact, her family’s less-than-regal starts have hung over Middleton since she stepped into the world of Britain’s moneyed and titled. Though hers is no Cinderella story — Middleton’s parents, who now run a successful party supply company, comfortably footed the $32,000-a-year bill for Marlborough boarding school — Commoner Kate is said to have long dreamed of the glass slipper. Friends at Marlborough reportedly even nicknamed her “princess in waiting.”

Middleton, however, seemed to get the last laugh at St. Andrews, the university in Scotland where she met and befriended William. The two then started dating, the story goes, after he was struck by her beauty as she modeled a sheer dress at a charity fashion show.

But she was to wait eight years before her prince finally popped the question, with a close call in 2007 when the couple separated. Some say Middleton grew tired of waiting for her prince, others say her background perhaps contributed to his initial lack of commitment.

accepting a commoner as the prospective mother of an heir to the British throne, the monarchy, many here say, is getting historically closer to its subjects. Middleton’s ascension could rekindle some of the lost spark between the crown and people, a cooling that only worsened after the death of Diana, Princess of Wales.

Middleton’s family tree is nevertheless presenting Queen Elizabeth II with a practical problem. Before the spring marriage, the queen will need to decide what title to grant Middleton, and Prince William reportedly is bucking for “Princess Catherine.”

Purists, however, note that in Britain, princesses are born, not made on paper. Diana, for instance, was known during her marriage to Prince Charles not as “Princess Diana,” but “Her Royal Highness the Princess of Wales.” Middleton may be expected to take her husband’s name, being officially known as “Princess William” in the manner of other commoners who have married lesser members of the British royal family.

“She can’t be called Princess Catherine because she isn’t a princess in her own right,” said Christopher Wilson, the London-based royal biographer. “She might be called that by the headline writers, but she won’t really be.”

Of course, given Middleton’s roots, the rising-above-her-station story line was always a headline waiting to happen. Much was made of Diana’s lack of royal bona fides, even though she was the daughter of an earl and hailed from one of the most pedigreed families in Britain.

At the time, the commoner label was wielded against Diana because she was not the progeny of a crowned head of Europe. Yet in upper-class British circles, the chatter about Diana’s lineage was almost always in self-mocking tones; few truly considered her a commoner.

Not so with Middleton. The rumor went that when she entered a room, some of Prince William’s friends would whisper “doors to manual,” a reference to her mother’s former career as a flight attendant. It is that sort of upper-crust dismissal of commoner blood that still shocks and stings many here.