Prince Harry, Meghan Markle and son Archie are on South Africa trip

Meghan Markle has a sweet nickname for her son Archie, which she recently revealed during the little royal's first-ever official engagement.

The Duke and Duchess of Sussex and son Archie stepped out as a family of three to meet South African human rights activist Archbishop Desmond Tutu and his daughter, Thandeka Tutu-Gxashe, reported People.

In a video from the visit, she is heard calling her son "Bubba".

"Say hello! Hello, hi," she said, and then realized he's drooling. "Oh, Bubba," she added.

She also called her son by the same nickname in a video that was shared on the couple's Instagram story as they walked down a corridor to meet with Archbishop Tutu.

Archie chuckled sweetly when Ms Thandeka laughed, to which she said, "Is that funny?". Ms Thandeka noted that Archie already seemed to understand her, to which Prince Harry said, "I think he knows exactly what's going on."

"You like me best, yes. Oh, you like the ladies better, yeah," Ms Thandeka said to Archie. Meghan agreed, "He likes to flirt."

Prince Harry also revealed that his son is "so busy, constantly wanting to stand."

"Exploring," Ms Markle added.

Archie seemed calm and happy throughout his first outing as he smiled at his hosts and played in his mother's lap.

After the outing, the royal couple posted a sweet black-and-white still of Archie on their Instagram, alongside the caption, "Thank you, Archbishop Tutu, for your incredibly warm hospitality, Archie loved meeting you!" It was signed "The Duke and Duchess."

The royal family was given gifts from Archbishop Tutu, including beautiful photos of Archie's late grandmother Princess Diana and children's books - Children of God Storybook Bible and Desmond and the Mean Word, both penned by the Archbishop and a children's songbook.

The Duke and Duchess also shared some behind-the-scenes clips of Archie's memorable first visit, including his high-five with Archbishop Tutu and a clip of him dancing in Ms Markle's lap. The video had "Oh Happy Day" playing in the background.

The family of three reached Cape Town, South Africa, on Monday as the Duke and Duchess of Sussex kicked off their 10-day tour, which includes stops in South Africa, Botswana, Angola and Malawi.

Ms Markle and Archie will stay in South Africa while Prince Harry will travel throughout Africa.

Ms Markle was spotted with Archie in her arms on Monday morning. In a tribute to late Princess Diana, Archie was seen wearing a white knit hat that was very similar to the one Diana chose for Harry to wear in January 1985 as they stepped off a plane in at Aberdeen Airport.