Prince William has given his daughter Princess Charlotte the nickname 'Mignonette'

In a video shared by Kensington Palace, the royal is seen asking his eldest son George as he swings on a rope swing: "What would you give it out of 10? How many marks out of 10 would you give it - 10 being the highest?"

George then replies: "Twenty!"

William jokes in response: "Twenty out of 10? That's pretty good. I think mummy's done well."

Then, referring to Charlotte, William says: "Mignonette? Give me a push."

'Mignonette' is derived from the French word 'mignon' which means meaning "small, sweet and delicate" or "cute".

William, 36, isn't the only one who has a nickname for Charlotte, and earlier this year it was revealed that Catherine, 37, has an adorable name for her daughter.

A Belfast blogger named Laura-Ann brought her son - also named George - to meet Kate and shared the entire encounter on her Instagram Stories

In the footage, Catherine says to the toddler: "Hello, what's your name? Hi George, what a cool name you've got, and you look very smart in your bow tie. It's very nice to meet you."

When Laura-Anne mentions she has another son Catherine enquires how old he is and when the blogger reveals he's four the royal says: "Oh, he's the same age as Lottie."