Prince Louishas a fun nickname from his mother,Kate Middleton!

The youngest son ofPrince Williamand Princess Kate may have beenabsent from the coronation concertSunday night, but he rejoined his parents and older siblings —Prince George, 9, andPrincess Charlotte, 8 — for hisfirst royal engagementwith the Scouts on Monday, where his mom let slip an adorable moniker.

While toasting marshmallows with the 3rd Upton Scout Group in Slough, the Princess of Wales was caught on video telling her son to discard a stick in the fire.

“Pop that in the fire, Lou Bug,” Katecould be heard saying.

DANIEL LEAL/POOL/AFP via Getty Images

Prince Louis of Wales enjoys a toasted marshmallow as he takes part in the Big Help Out, during a visit to the 3rd Upton Scouts Hut in Slough

The royals are no strangers to nicknames (Prince Harry’s real name is Henry and Kate’s full name is Catherine), so it’s no surprise that they have other monikers for each other at home.

While it was the first time hearing “Lou Bug,” Kate has called her children sweet nicknames in the past. It’s previously been revealed that the royal momcalls Princess Charlotte “Lottie"and “Poppet.” And during a2018 visit to Leicester, it was revealed that Prince George calls his dad “Pops.”

Prince George of Wales, Britain’s Prince Louis of Wales and Britain’s Catherine, Princess of Wales toast marshmallows as they take part in the Big Help Out, during a visit to the 3rd Upton Scouts Hut in Slough

In another adorable moment when a scout member handedPrince Louisa s’more to eat, the royal mom-of-three reminded the young prince to give his thanks: “What do you say?” she said, to whichPrince Louisresponded, “Thank you.”

Prince William, Prince George, Princess Charlotte, Kate Middleton and Prince Louis.DANIEL LEAL/POOL/AFP via Getty Images

Catherine, Princess of Wales, Britain’s Prince William, Prince of Wales, Britain’s Prince George of Wales, Britain’s Prince Louis of Wales and Britain’s Princess Charlotte of Wales pose for a group pictures with volunteers who are taking part in the Big Help Out, during a visit to the 3rd Upton Scouts Hut in Slough

Prince LouisandPrince Georgechanneled their mom, who wore a light blue button-up blouse with black pants. The two princes wore different shades of blue polo shirts, withPrince Louispairing the look with dark blue long shorts andPrince Georgedonning green jeans pants.

Prince Williamdonned a dark blue long-sleeved button-up shirt with dark black pants, asPrincess Charlottewent with lighter colors for the event, sporting a light pink shirt with a collar over a dark pink sweater and shorts. All the members of the Wales family also wore yellow and burgundy scarves around their necks.

Prince Louis.DANIEL LEAL/POOL/AFP via Getty Images

Prince Louis of Wales uses his hand to make a paint decorations on a wall while taking part in the Big Help Out, during a visit to the 3rd Upton Scouts Hut in Slough

“Louis was very enthusiastic and did a good job,” said Anne Edwards, an adult Scout helper who worked with Charlotte and Louis to paint cinder blocks to support wooden planters.

Edwards saidPrince Louis' older sister was there to keep an eye on her sibling the whole way through.

“She was advising him, obviously! ‘Don’t do that, Louis!’ — things like that,” Edwards says, adding that seeing the Wales children so enthusiastic about the effort was lovely.

Prince Louis of Wales takes control of a wheelbarrow as he helps his mother, Britain’s Catherine, Princess of Wales take part in the Big Help Out, during a visit to the 3rd Upton Scouts Hut in Slough

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He was also spotted moving a wheelbarrow with what appeared to be soil in it and helping to shovel out some of its contents, and in several other photos, he and his brother could be seen taking turns on their father’s lap asPrince Williamnavigated a tractor.

“They were very relaxed and joining in, like normal kids. That was what was really nice about it,” the volunteer said.

source: people.com