Which pseudonym did J.K. Rowling use for the Quidditch book sold for charity?

J.K. Rowling used the pseudonym Kennilworthy Whisp for the charity book Quidditch Through the Ages.

Quidditch Through the Ages was published in 2001 as a fictional reference work about the history and rules of the wizarding sport. Within the Harry Potter world, it is presented as a book borrowed by Harry from the Hogwarts library and written by the fictional Quidditch expert Kennilworthy Whisp.

The real-world edition was published alongside Fantastic Beasts and Where to Find Them to raise money for Comic Relief. The books were designed as companion volumes rather than installments in the main Harry Potter narrative. Their proceeds supported charitable work, and both imitate the style of books found inside the fictional wizarding world.

Readers can confuse Whisp with Newt Scamander, the credited fictional author of Fantastic Beasts and Where to Find Them, or Bathilda Bagshot, the historian associated with A History of Magic. Kennilworthy Whisp is specifically linked to the history of Quidditch.