C.S. Lewis’s dog was named Jacksie. Lewis discussed the dog and the origin of his own nickname in his autobiographical book Surprised by Joy, published in 1955.
When Lewis was a child, he and his brother Warren had a dog named Jacksie. After the dog was killed in an accident, Lewis reportedly insisted that he would answer only to the name Jacksie. The name was later shortened or transformed into “Jack,” which became his familiar lifelong nickname.
Surprised by Joy is not a conventional day-by-day autobiography. Instead, it traces Lewis’s intellectual and spiritual development, including his movement from childhood belief to atheism and later Christian faith. The childhood dog episode helps explain a name that can otherwise seem unrelated to “Clive.”
Some accounts spell the dog’s name as Jacksie, while casual retellings may focus only on the later nickname Jack. The canonical name associated with the episode in Lewis’s autobiography is Jacksie.