Princess Anne's Bizarre Nickname For King Charles Speaks Volumes About Their Relationship

While the public knows them by their formal titles, the British royal family often use nicknames when addressing each other behind closed doors. For example, it's common knowledge that the late Queen Elizabeth II was adorably nicknamed Lilibet in childhood, a moniker that was controversially given to Prince Harry and Meghan Markle's daughter. As it turns out, Princess Anne also has a special nickname for her older brother, King Charles III.

A behind-the-scenes clip from the BBC documentary "Charles III: The Coronation Year" shows the princess royal approaching King Charles amid coronation preparations. "Hello, old bean," Anne says in greeting, eliciting a laugh and a kiss on the hand from her brother. The moment speaks to the close connection shared between the two royals, who grew up as Queen Elizabeth's eldest children.

"They have this very warm relationship," royal expert and editor Hannah Furniss told The Telegraph. "She is probably in a better position than anyone to give him advice, give him a bit of sympathy when he needs it, give him a bit of a pep talk." While nicknames alone suggest a degree of familiarity, the meaning behind "old bean" may reveal something else about the two royals and their connection.

It may strike Americans as strange that Princess Anne greeted King Charles as "old bean," but the nickname has English roots similar to the "poppet" endearment that Kate Middleton was heard calling Prince Louis. The Cambridge Dictionary defines "old bean" as "a friendly way of talking to a man." The colloquialism also has an air of poshness to it and is typically used between men, which might be in part why King Charles found Princess Anne's address so humorous.

In 1998, the princess royal became the first woman to hold the title of Colonel of the Blues and Royals, dressing in her ceremonial military uniform for the coronation. In this position, she also served as the king's Gold Stick in Waiting, the primarily ceremonial role of the monarch's personal bodyguard.

"That is a role I was asked if I'd like to do for this coronation, so I said yes," the princess royal told CBC News. "Not least of all, it solves my dress problem." Given that Princess Anne has been caught breaking plenty of rules in the name of gender equality, it's no surprise that she'd playfully reference her traditionally masculine role in her lighthearted address to her brother. On top of this, it serves as a peek into how bonded the two royal siblings really are.

When Princess Anne was caught calling King Charles III "old bean," royal experts reported that the familiar address spoke to the closeness of their relationship. As the oldest of Queen Elizabeth's children, King Charles and Princess Anne are only 21 months apart and quite a few years older than their two younger brothers.

While King Charles and Princess Anne's childhoods differed significantly, their age proximity reportedly bred an early closeness between the royal siblings. "Both of them grew up in the 1960s, where you had this social change within the United Kingdom, within the world, people being freer, but you still have the constraints of the monarchy," royal historian Marlene Koenig told Business Insider.

This bond has only become more important since Charles assumed his role as king, with Princess Anne becoming a significant confidante for her brother. "She is the person the King has known longest," Wesley Kerr, royal commentator, told Tatler. "She can be relied on for complete discretion and unconditional love." While "old bean" might not seem like the cutest nickname at first glance, it speaks volumes about the relationship between Princess Anne and King Charles.