Update, April 27: Kensington Palace has finally confirmed the name of Prince William and Kate Middleton's third child. "The Duke and Duchess of Cambridge are delighted to announce that they have named their son Louis Arthur Charles," the palace stated on Instagram. "The baby will be known as His Royal Highness Prince Louis of Cambridge."
Per The New York Times, Prince Louis was named after one royal family member in particular: Prince Charles's uncle, Lord Louis Mountbatten. "Louis is Prince William’s fourth name and was apparently chosen by his father, Prince Charles, as a tribute to Lord Louis Mountbatten, a mentor of Prince Charles’s, a prominent British naval officer and the Duke of Edinburgh’s uncle," the NYT explains. Congratulations again to the adorable new family of five.