Royal infants mostly have safe, historical names which are passed down through the monarchy, with bookmaker William Hill reporting George as the favourite for a boy and, after a flurry of bets, Alexandra - one of the Queen's middle names - as the favourite for a girl, while Charlotte is also thought to be a contender.
Elizabeth, in tribute to the Queen, and Diana, to pay homage to William's late mother, are also expected to make an appearance if the baby is a girl, while Charles, in honour of the Prince of Wales, or Philip, for the Duke of Edinburgh, are possibilities if it is a boy.
The Cambridges are also likely to take inspiration from Kate's side of the family, perhaps honouring her father Michael or mother Carole.
Francis is a recurring name in Kate's family tree. It is both her father and her grandfather's middle name and Frances was her great-great-great grandmother's first name. It was also William's mother's middle name.
The Queen will undoubtedly be informed of the chosen names prior to their announcement, but is unlikely to wield a veto.
Royal writer Christopher Warwick said: "The Queen is so down to earth that she's not likely to jump up and down and say this boy has got to be called Charles and George.
"This isn't going to be 'Granny, do you approve?' but more 'These are the names we've chosen - do you like them?'.
"It's much more of a personal thing these days."
It is unlikely, however, that William and Kate would pick a name out of keeping with royal tradition, and they will be mindful of choosing a name that befits a future king or queen.
In the past, the approval of the sovereign has held great importance.
When the Duke and Duchess of York had their second daughter Princess Margaret Rose in 1930, they were planning to call her Ann Margaret, but changed their mind after learning that King George V disliked the name Ann.
Queen Victoria insisted that the name Albert be used as a middle name, if not a first, in honour of her beloved consort Prince Albert.
The Duke and Duchess of York took people by surprise in 1990 by naming their daughter Eugenie - a little-known name but one that has royal connections to Princess Victoria Eugenie of Battenberg.
The name of William and Kate's baby could come to symbolise an entire era, as in Georgian, Victorian and Elizabethan.
Royal babies' names are not usually revealed straight away and the public are often left guessing for several days as speculation mounts.
When Princess Beatrice was born in 1988, it was two weeks before her name was known.
When William arrived in 1982, his parents waited seven days before deciding upon and announcing his name. Diana was thought to have preferred names such as Sebastian and Oliver, while Charles was reportedly holding out for Albert.
Charles's own name, however, remained a mystery for an entire month and was only declared ahead of his christening in the Music Room of Buckingham Palace in December 1948.
In a more modern approach, William and Kate could buck the trend and unveil their chosen name immediately.
Royal babies tend to be given a number of middle names.
The Prince of Wales has four names - Charles Philip Arthur George - while the Duke of Cambridge also has four - William Arthur Philip Louis.
The Queen has three names - Elizabeth Alexandra Mary - while William's mother Diana, Princess of Wales, was Diana Frances.
The Duchess of Cambridge has just two names, Catherine Elizabeth.
Prince Harry's first name is actually Henry, followed by Charles Albert David.
King Edward VIII, who abdicated the throne, had seven names - Edward Albert Christian George Andrew Patrick David - but was always known to his family as David.
Queen Victoria was named Alexandrina Victoria and as a child was nicknamed Drina.
If the baby is a boy, he will be styled a Prince and, thanks to a new letters patent issued by the Queen, if the baby is a girl, a Princess.
When William was born he was Prince William of Wales and his children will use Cambridge in the same way, becoming HRH Prince (forename) of Cambridge or HRH Princess (forename) of Cambridge.
According to the monarchy's official website: "For the most part, members of the Royal Family who are entitled to the style and dignity of HRH Prince or Princess do not need a surname, but if at any time any of them do need a surname (such as upon marriage), that surname is Mountbatten-Windsor."
In 1917, George V adopted Windsor as the royal family's House and surname.
In 1960, for the direct descendants of the Queen and the Duke of Edinburgh who require a surname, it became Mountbatten-Windsor.
Mountbatten was the surname Greek-born Prince Philip assumed when he became naturalised in 1947.
If a boy, the baby is also likely to one day be Prince of Wales when William accedes to the throne. The title is usually given to the male heir to the throne, but it is not automatic.
Royal birth a contrast to history
As the world awaits the delivery of the Duke and Duchess of Cambridge's baby, this royal birth stands in marked contrast to the arrival of past kings and queens, according to one historian.
Judith Rowbotham described how during Queen Victoria's reign royal pregnancies were not publicly discussed, whereas Kate's was announced when she was just two months pregnant.
Confirmation that the Duchess is in hospital also means the nation is aware that Kate is in labour - something that was inconceivable when the last granddaughter-in-law of a reigning queen to give birth to a future monarch did so in the 1890s.
George V's wife Mary of Teck, who was then the Duchess of York, had the future Edward VIII in 1894 and the future George VI in 1895, but news of her "confinement" was limited.
Dr Rowbotham, a social historian at Nottingham Trent University, said: "Pregnancy was not something that was publicly talked about then. It wasn't discussed. It was indelicate.
"We didn't notice women's physicality in that way because it implied women were having sex."
She added: "With Queen Mary of Teck, who was the Duchess of York, there was notice taken. It was mentioned, but more implied than discussed. There was reference to how she 'looked in blooming health'."
It was noted that Mary was missing from social events that she normally attended, but there was no in-depth discussion about the pregnancy or speculation about baby names as with William and Kate's baby.
Dr Rowbotham added: "The media was more discreet and more reverential."
Future monarchs were also traditionally born at home, with only people who were not well off having their babies delivered in hospital.
"You didn't go to hospital in those days to give birth because maternity wards were for the poor," Dr Rowbotham said.
William was the first future King to be born in hospital, when reporters were also told that Diana, Princess of Wales, had been admitted and was waiting to give birth.
The Queen, however, had all her four children at home at Buckingham Palace and Clarence House.
Kate will also be spared the humiliating age-old custom of having a government minister present when she gives birth.
Dr Rowbotham revealed: "There was scrutiny until Queen Victoria put her foot down... There used to be a representative in the room seeing the child delivered. They stood to the side so that they wouldn't get a view of the royal private parts."
In 1688, James II and Mary of Modena produced a son and heir - James Francis Edward - after 15 years of marriage.
Mary of Modena was forced to give birth to an audience of dozens of witnesses including the Archbishop of Canterbury and ministers of state, ambassadors and key family members.
But it was still rumoured that the baby was actually a changeling who had been smuggled in a warming pan to ensure the restoration of Roman Catholicism.
According to tradition, several Privy Counsellors and Ladies in Waiting used to be in attendance in an adjoining room.
In 1894, Queen Victoria declared that for the birth of her great grandchild, the future Edward VIII, only one Cabinet minister would be needed, with only the Home Secretary attending from then on.
The birth of the Queen's cousin, Princess Alexandra, in 1936 was the last occasion on which the Home Secretary was present.
King George VI declared that a minister was needed only for those in the direct line of succession, but by the time the Prince of Wales was born in 1948, the practice had been abandoned.
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