The Queen no longer goes by her childhood nickname Lilibet after the passing of her husband Prince Philip, who was the last person to use it.
It was fondly adopted as a moniker by the Queen's grandparents and parents during her early childhood when she struggled to pronounce her name, calling herself " Lilibet " instead.
She would often sign off letters with the shortened version of Elizabeth, including in a thank you note addressed to her grandmother Queen Mary, the Daily Star reports.
It reads: "Darling Granny. Thank you very much for the lovely doll's house. I do love it, and I have unpacked the dining room and the hall. Love from Lilibet xxx."
Her father, George VI, is quoted as saying: "Lilibet is my pride. Margaret is my joy."
In a handwritten note left on the Duke of Edinburgh's coffin at his funeral last year, the Queen appeared to have signed it from Lilibet.
But although the sweet pet name was used by her older family members and by her husband, no one else in the Royal Family refers to her as Lilibet.
In homage to the Queen, Prince Harry and Meghan Markle gave their one-year-old daughter, who was born in California and has dual US and UK citizenship, the nickname.
During the Platinum Jubilee celebrations last week, the Queen finally got to meet her granddaughter and namesake.
The long-awaited family reunion reportedly took place at Windsor Castle within 48 hours of the Sussexes returning to the UK.
The couple, who also have three-year-old son Archie, released a new photo of Lilibet in Windsor last week to mark her first birthday.
Harry and Meghan had reportedly asked for a private photographer to be present at the meeting between the Queen and Lilibet.
However, the Queen reportedly told them "no chance" when asked her opinion on the matter - due to fears the images would be leaked to US television networks.
The Sussexes were noticeably absent from the limelight during the Platinum Jubilee celebrations and were spotted sitting several rows behind Prince Charles and Prince William during Friday's Service of Thanksgiving at St Paul's cathedral.
Harry and Meghan were pictured watching Trooping the Colour from a window but were not part of the carriage procession or the group of working royals permitted on Buckingham Palace's balcony.
There are several other sweet names that the Queen's children, grandchildren and great-grandchildren use for her.
Her Majesty is called "Mummy" by Prince Charles, who referred to her as this during his speech for her 92nd birthday, which saw her roll her eyes and laugh along with the amused audience.
William and Harry were spotted cheering on "Granny" as her stunt double parachuted into the stadium during the 2012 Olympics.
And it was revealed by the Duchess of Cambridge that Prince George and Princess Charlotte call her "Gan-Gan".
