Prince Harry and Meghan Markle (opens in new tab) delighted royal fans (and the rest of the royal family (opens in new tab)) this weekend with the announcement that they are expecting their second child.

The Duke and Duchess of Sussex (opens in new tab) broke the news in a brief announcement (opens in new tab) on Sunday. Harry and Meghan shared several important details about her, including her birthday (born Friday, June 4), her weight (7 pounds, 11 ounces), and of course her name: Lilibet "Lili" Diana Mountbatten-Windsor.

Harry and Meghan (opens in new tab) chose this unique name in honor of Queen Elizabeth II (opens in new tab) and Harry's late mother, Princess Diana (opens in new tab). As the couple explained in the birth announcement, "The name Lili is in honor of our great-grandmother, Her Majesty the Queen. Her middle name, Diana, was chosen to honor her beloved late grandmother, the Princess of Wales."

The name Diana was chosen to honor her beloved late grandmother, the Princess of Wales.

For those who are unfamiliar with the Queen's lovely nickname, here is a little background.

It is a well-known fact among royal fans that Lilibet (open in new tab) is the Queen's childhood nickname, but not many people know the origin behind this unique nickname. So who bestowed this endearing nickname on the future monarch? Hello! (opens in new tab) magazine (opens in new tab), she was unable to pronounce "Elizabeth" as a child and probably pronounced her name as "Lilibet."

As a child, the Queen's parents and grandparents called her Lilibet, and her father, King George VI, once said of the Queen and her sister, Princess Margaret, "Lilibet is my pride. Margaret is my joy."

The nickname was also accepted by the queen, and Elizabeth was known to sign notes to loved ones "Lilibet."

"Darling grandmother. Thank you for the lovely doll house. I have unpacked the dining room and hall. Love from Lilibet xxx," he wrote in a letter to Queen Mary (opens in new tab), written as a child.

While this has always been one of the Queen's nicknames, the last known person to call her Lilibet was her late husband, Prince Philip. In fact, the Queen reportedly signed this nickname in a note (opens in new tab) attached to his coffin at her funeral this spring.

Now, of course, the sweet nickname and its endearing backstory and legacy will live on through her great-grandson, Lili.