LONDON — Lilibet “Lili” Diana Mountbatten-Windsor may be only 3 days old, but her name — chosen to honor two of Britain’s most famous royal women — is already one that people won’t forget.

Parents Meghan and Harry, Duke and Duchess of Sussex, announced the birth of their daughter on Sunday. They described her arrival Friday as “more than we could have ever imagined,” adding that they were “blessed” to welcome a second child together.

The baby, who weighed 7 pounds, 11 ounces and is settling in at the family’s California home, is named after Queen Elizabeth II, Harry’s 95-year-old grandmother, and Diana, Princess of Wales, Harry’s mother, who died in a car crash in 1997 at age 36.

But why was the queen nicknamed “Lilibet” by those closest to her, and where did the unique name come from?

As a young girl growing up in the royal family, then-Princess Elizabeth found it difficult to pronounce her name, often fumbling it — much to the amusement of her close family members, who soon began calling her “Lilibet,” according to British media. The affectionate moniker has stayed with her throughout her long life.

During her childhood, Elizabeth often wrote letters to her grandmother, Queen Mary, as a means of staying in touch. In one letter, the young princess described a recent party she had attended, recalling the day with childhood delight.

“It was simply lovely,” 7-year-old Elizabeth wrote. “There was a clown and a jester and a snowman.” She signed off the letter to her grandmother with “Love from Lilibet.”

The nickname was later adopted by the queen’s husband, Prince Philip, who wrote shortly after the two were married in 1947 that “Lilibet is the only ‘thing’ in the world which is absolutely real to me,” in a note to the queen mother.

At the funeral of the queen mother in April 2002, Elizabeth left a floral wreath tribute atop the coffin, alongside a note that read: “In loving memory, Lilibet.”

When Prince Philip died at age 99 in April, British media speculated that the queen’s handwritten tribute to her husband of more than seven decades was also signed affectionately with “Lilibet,” although the note’s placement was partially obscured by white floral tributes, making it impossible to confirm exactly what was written.

The double-barreled surname Mountbatten-Windsor is a combination of both the queen’s and Philip’s last names when they married.

Reaction to the baby’s name from the British tabloids Monday morning was mixed. The Metro newspaper labeled the tribute to the queen a “Gran Gesture,” while the Daily Mail pondered whether the pair had asked the reigning monarch for permission before the name was publicly announced.

“New baby Sussex given queen’s family nickname (but did they even ask her?),” the paper said on its front page.

On social media, many Britons praised the pair’s decision to pay tribute to both women through the latest royal’s name. One of many congratulatory tweets described their action as a “beautiful gesture,” while another commenter wrote: “Grandmother Diana would be proud.”

Despite what has been a testing time for Britain’s royal family, following a string of accusations from Meghan and Harry that they were not treated well by the institution and faced racism and neglect from family members who did not protect them from incessant hounding of the British tabloids, senior royals led the well wishes pouring in on Sunday.

The entire family said it was “delighted with the news,” including Harry’s father Prince Charles. The prince and Diana divorced a year before her death in Paris.

“Congratulations to Harry, Meghan and Archie on the arrival of baby Lilibet Diana,” Charles and wife, Camilla, Duchess of Cornwall, tweeted Sunday. “Wishing them all well at this special time.”

Lilibet is the queen’s 11th great-grandchild and is eighth in line to the British throne, after big brother Archie Harrison, who is seventh. Her arrival knocked Prince Andrew down to ninth place in the line of succession.

Like her brother, Lilibet is set to possess dual citizenship. Given that she was born in the United States, she automatically qualifies for American citizenship and can claim British citizenship through her father Harry, who was born in London.

Archie, however, was born in Britain, so he is automatically considered a British citizen but can claim American citizenship through mother Meghan as she is a citizen.

Unlike their cousins, Prince George, Princess Charlotte and Prince Louis, Archie and Lilibet do not hold a prince or princess title.

When he was born, George was given the title of prince because he was third in line to the British throne — meaning he automatically qualified for the title unlike his siblings. The queen then stepped in to make Charlotte and Louis a princess and a prince, with all three being the children of a future king.

The issue of titles has seemingly been a stumbling block for family members, with Meghan telling Oprah Winfrey that she was worried her children would not get the adequate security protection that comes with such a title.

While British media has speculated that the Sussex siblings might never hold titles, other reports have floated the idea of Charles bestowing titles to the children once he becomes king and has power to issue titles or change the current Letters Patent.

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