Reference for the first name of Neville Longbottom's grandmother: Augusta Longbottom

Question

Similarly to Reference for the first name of Sirius Black's mother, known from her portrait: Walburga , I'm asking about the name of a character whose first name doesn't seem to be mentioned in the books.

Neville Longbottom was raised by his grandmother. She is mentioned many times in the books, first in Harry Potter and the Philosopher's Stone chapter 7. We see more about her in Order of the Phoenix chapter 23 and Deathly Hallows chapters 29 and 31. From Order chapter 23, we even learn she is Frank Longbottom's mother.

Granny's name is given as Augusta Longbottom on some websites. Is this canon? What is the primary source of this name? Does it appear in the books? Movies? Movie credits?

Answer 1

Her name was confirmed at least in Half-Blood Prince chapter 9 by prof McGonagall, when she discusses with Neville what subjects he should take.

‘My grandmother thinks Charms is a soft option,’ mumbled Neville.

‘Take Charms,’ said Professor McGonagall, ‘and I shall drop Augusta a line reminding her that just because she failed her Charms O.W.L., the subject is not necessarily worthless.’

Answer 2

Out of universe, JKR confirmed the name in a cast interview (as well as giving a bit of extra back-story about her confrontation with John Dawlish):

SU: You know, Jo, he idolizes a man, an auror guy who got pwned by an old lady wearing a dead bird on her head, you know, on her hat. Now, come on!

JN: They don't understand this, Jo. I know we've talked about this. They don't understand the night that this-- They call it a duel. It wasn't a duel. At least in my mind anyway, I think it needs a little explaining of how somebody as, you know, as skillful as Dawlish, you know, could've got taken down like this.

...

JKR: By the time Augusta Longbottom got to him, he had been-- several people had attacked Dawlish. I mean, I think he was a bit punch-drunk by that point, you know. He had become a favorite punch-bag of the Order of the Phoenix by then. So I don't think he was firing on all cylinders. But I really saw Mrs. Longbottom as a powerful witch. So, um, sorry. - Pottercast Interview

The actress portraying the character in the film also explicitly named her;

Our friends at Snitch Seeker have confirmed that actress Ninette Finch was cast as Neville Longbottom’s grandmother in Deathly Hallows. Finch was also involved in Half-Blood Prince as an extra. ”Yes I am playing Augusta Longbottom, although it is not a very big part… I have also played a couple of witches and was one of the people on the Millennium bridge when it was under attack,” Finch said.