While he may go by several different names: His Royal Highness, William of Wales, and Wills, but the name his wife favors is "Big Willy." The couple each has a nickname for the other; Kate's is "Babykins."
William's nickname was inadvertently revealed when he posted photos of a "day in the life" while he was at work at the Royal Air Force base. His coffee mug has the words "Big Willy" imprinted on it, and gave rise to the nickname, which The Daily Star claimed was given to him by his wife.
He has had a slew of nicknames, stemming from his childhood. At one point, his mother, the late Princess Diana, called him "Willy Wombat," given his love for the animal. In everyday life, though, he either went by William or "Wills," a name generally reserved for friends and family.
Kate, meanwhile, revealed during a visit to her childhood school that her nickname was once "Squeak."
"I was nicknamed Squeak just like my guinea pig. There was one called Pip and one called Squeak because my sister was called Pippa and I was Squeak," she told students at St. Andrews. That, perhaps, is one of the nicer nicknames Kate has had throughout her life.
At one point in her relationship with William, she was referred to as "Waity Katie" for going out with him for so long and not receiving a marriage proposal. Their relationship was on-again, off-again so often that the press, and some peers, gave her the unfortunate nickname.
Both royals have been busy preparing for their own little one, whose gender and future nickname have yet to be revealed. William and Kate recently placed an advertisement for domestic help once the baby arrives this summer. The couple will buck tradition yet again by not having an entire household of help but instead just rely upon one or two persons.