This was the hat worn by Augusta Longbottom.
In a 1993 Defence Against the Dark Arts class at Hogwarts School of Witchcraft and Wizardry, third year students were taught how to defend themselves against boggarts. When a boggart was released to Neville Longbottom, it assumed the form of Severus Snape. Remus Lupin, who was teaching the class, told Neville to picture Snape in his grandmother's clothes. Neville cast Riddikulus, and the boggart was wearing his grandmother's clothes, including her vulture hat.