The author wrote: "The Naga are snake-like mythical creatures of Indonesian mythology, hence the name Nagini...
"They are sometimes depicted as winged, sometimes as half-human, half-snake. Indonesia comprises a few hundred ethnic groups, including Japanese, Chinese and Betawi. Have a lovely day."
Diversity has long been a topic attached to the book series as it has previously been pointed out that Dean Thomas, Lee Jordan, Cho Chang, Angelina Johnson, Kingsley Shacklebolt, and Padma and Parvati Patil are the only people of colour in the novels.
Earlier in the week, when fans began to tweet their reactions, J.K. Rowling gleefully responded, showing no surprise that people were shocked. She also cleared at least one thing up: Nagini is not an Animagus.
In the Harry Potter universe, Animagi are skilled witches and wizards who can transform into animals at will.
"Not an Animagus. A Maledictus. Big difference," Rowling tweeted.
Fantastic Beasts: The Crimes Of Grindelwald, the sequel to 2016's Fantastic Beasts And Where To Find Them, sees Eddie Redmayne return as Newt Scamander, while Jude Law plays a young Albus Dumbledore.
The Maledictus is new to the Harry Potter universe. The term was first introduced on Pottermore, Rowling's Potter-themed website, but details were scarce. At the time, it was only said that there was a new, "mysterious character played by Claudia Kim".