The Duke and Duchess of Sussex are expecting their first baby any day now.
And the name Allegra has dramatically moved up to sixth in the baby name stakes by Ladbrokes after a flood of bets over the past 24 hours.
It has led bookmakers to slash odds from 100/1 to 12/1.
Diana remains the favourite, while Allegra is making up ground having reportedly been the princess’ favourite name if she had had a daughter.
Grace is another frontrunner with Diana, both are 6/1 with bookies while Arthur and Elizabeth are 8/1.
Traditional names are very much in fashion and that is reflected with Albert and Victoria both standing at 16/1.
A Ladbrokes spokesman told the Daily Mail: “We’re scratching our heads as to why we’ve seen so much interest in Allegra.
“The bets are coming in thick and fast and it’s been by far the most popular pick of the month with punters.”
It was reported by the Evening Standard in 2004 that Allegra was Princess Diana’s favourite name and she is claimed to have said it sounded “beautiful” when her pal Lady Annabel Goldsmith said it.
The source said: “The princess was desperately in love with Hasnat Khan. She was even talking about marrying him and having his baby. It was her dream.
“She thought of a name for her, Allegra, after her friend Lady Annabel Goldsmith mentioned it. She heard the name and thought it was beautiful.”
The Duke and Duchess of Cambridge chose traditional names for their children and Meghan and Harry could still opt for names that are more unusual.
William and Kate are parents to Prince George, five, Princess Charlotte, three, and Prince Louis, who was born in April.