The Duke and Duchess of Cambridge welcomed Louis on Monday, officials at Kensington Palace confirmed, weighing in at eight pounds, seven ounces.
He is fifth in line to the throne, and the sixth great-grandchild of 92-year-old Queen Elizabeth.
Most royals have three to four first names, usually in a combination that honours previous monarchs or relatives. William and Kate’s firstborn is named George Alexander Louis and his sister is Charlotte Elizabeth Diana — honouring both her great-grandmother Queen Elizabeth II and her late grandmother, Diana, Princess of Wales.
British bookmaker William Hill had Arthur as the most likely name for the Royal baby with 12-1 odds.
James was also among bookmakers’ favourites for the new prince, whose full title will be His Royal Highness, Prince Louis of Cambridge.
William made a joke with fans this past week about naming his son after Aston Villa footballer Jack Grealish, which brought the odds for the name Jack upwards from 50/1.
The three names are popular ones, often recycled in the royal family. Prince Charles’ full name is Charles Philip Arthur George, while Prince William’s is William Arthur Philip Louis. Prince George’s full name is George Alexander Louis.
Lord Louis Mountbatten was Prince Charles’ great-uncle, who was assassinated by the IRA in 1979. Prince Louis of Battenberg was the Duke of Edinburgh’s grandfather’s name.
Louis is a French name, meaning “famous warrior.” (Fun fact: 18 French kings have had this name.)
As for Arthur, the name is legendary in England, as it references King Arthur, who ruled in the late 5th century (AD).
When William was born, it took a full week before his name was announced, but the names of George and Charlotte were announced within two days of their births.
Louis was delivered at St. Mary’s Hospital in London, where his siblings Prince George, 4, and Princess Charlotte, 2, were delivered in 2013 and 2015, respectively. Both William and Prince Harry were also born there.
William was present for the birth of his son.
The palace said, “the Queen, the Duke of Edinburgh, the Prince of Wales, the Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news.”
—With files from Chris Jancelewicz