What is the name of Digory Kirke's eccentric uncle in The Magician's Nephew?

Digory Kirke's eccentric uncle in The Magician's Nephew is Andrew Ketterley.

Usually called Uncle Andrew, Andrew Ketterley is a self-styled magician living in London. He experiments with magical rings made from mysterious dust associated with his godmother, Mrs Lefay. Rather than testing the rings himself, he tricks Polly Plummer into using one and then pressures Digory to follow her with another, sending the children into the Wood between the Worlds.

Uncle Andrew's experiments trigger the book's major events. Digory and Polly encounter Jadis, the future White Witch, and accidentally bring her to Earth before reaching the newly created Narnia. Andrew is present when Aslan creates the world, although his fear prevents him from understanding or hearing the animals properly.

The character is not Dr. Cornelius, who appears in Prince Caspian, and “Cornelius” alone is not the canonical name here. Andrew later gives up active magic, but his rings help connect the story to the wardrobe's origin and to Digory's future as Professor Kirke.