Prince Harry and Meghan Markle’s unique but simple nickname for their son, Archie, has just been revealed.

This week, it was reported that the Duke and Duchess of Sussex made a secret donation to marine conservation charity Love the Oceans on Just Giving under the name of their son. The royal couple donated £4,350 or $5,424.

According to Harper’s Bazaar, the donation will be used to help the charity build a swimming pool in Guinjata Bay Mozambique. Love the Oceans was aiming to raise £5,000 to teach 200 children how to swim with the help of eight swimming assistants and one swimming teacher.

Adam Knight, one of the collaborators with the charity, said that he had a gut feeling that the donation was made by Prince Harry and Markle under their son because the initials of the person who donated were HMW. Archie’s full name is Archie Harrison Mountbatten Windsor.

“We made some calls and were able to verify that it was from them, which is just incredible. Without that donation and support this would not be happening,” Knight said.

According to Express, Prince Harry and Markle most likely made the donation after they saw the charity on Instagram. Knight also said that he started working with the charity last summer.

“It was a little nerve-wracking going out [in the water] with just one other person, but I thought, ‘We’ve got a whole community of children that don’t know how to swim.’ There’s a scuba diving resort with a swimming pool—let’s do something with this, let’s change things,” he said.

Meanwhile, Prince Harry and Markle also made headlines this week after it was revealed that they will be traveling to South Africa on Sept. 23. The royal couple’s overseas tour will end on Oct. 2. After their arrival in Cape Town, Prince Harry will embark on his solo engagements in Malawi, Angola, and more.

An official christening photo released by Prince Harry and his wife Meghan, holding their baby son, Archie at Windsor Castle
An official christening photo released by Prince Harry and his wife Meghan, holding their baby son, Archie at Windsor Castle SUSSEXROYAL / Chris ALLERTON