Prince William and Kate Middleton are married for almost a decade now. But, there were only a few instances when the public witnessed and saw their public display of affection. This is why when they do something sweet before the public, everyone seemingly goes excited to know more about it.

It is not surprising, though, given that they are senior members of the British Royal Family. Not to mention, the Duke and Duchess of Cambridge are some of the most "regal" royals in recent times. This is also the reason why they seem too formal on every account, not just in showing affections but, in calling each other as well during engagements.

According to Cheat Sheet, there is a reason why Prince William calls Kate Middleton, "Catherine," especially when they are in public. As revealed, the Duchess went by this name in her high school years. However, she "shorted" it upon entering college at St. Andrews University.

It is worth noting that this is where the Cambridge couple met and started to date. During those years, she went by "Kate."

Royal experts and commentators, reportedly, shared that it is more "royal" when members of the Royal Family use their full names. So, after marrying each other in 2011, the future Queen, reportedly, "rebranded" herself as Catherine.

This did not stick, though, with the public. Although her full name is used to address her formally, royal fans and watchers have remained fond of calling her "Kate."

As for Prince William, it was said that he calls Kate Middleton by her full name to provide his wife the "reverence she has earned." Nothing more, nothing less.

In a related report released by Grazia Daily UK, sources stated that the Duke and Duchess may seem formal when in public but, they actually call each other by nicknames in private. Just like any couple, it was revealed that they, too, have "cute" names for each other.

As claimed by the source, there was an incident before when Kate Middleton "accidentally" slipped the nickname she calls her husband. It was shared that she referred to him as "babe," despite having an audience for an interview.

It was seemingly the first and only incident when the Duchess was heard to call Prince William her "babe." So, it was not surprising that it became a talk of the town during that time.

But, aside from their full names and "babe," it was shared that the Duke also calls his wife "Poppet." He was, reportedly, heard by the press and fans when they stepped out of the Lindo Wing at St Mary's Hospital to present Prince George to the public.