C.S. Lewis’s full first name was Clive, although he was widely known as Jack. His complete name was Clive Staples Lewis, and “C.S.” came from his first two initials.
Lewis adopted the name Jack during childhood after the death of a childhood dog named Jacksie. He reportedly began calling himself Jacksie, which later became Jack. The nickname remained with him throughout his adult life, and friends, family, and colleagues generally used it instead of Clive.
The name Charles is sometimes associated with Lewis because of his initials or because he was a prominent Christian writer alongside figures such as Charles Williams. However, Charles was not his first name. Lewis was born in Belfast in 1898 and became a scholar of English literature, a novelist, and a Christian apologist.
His best-known works include The Chronicles of Narnia, The Space Trilogy, and The Screwtape Letters. “Jack” identifies the private man, while “C.S. Lewis” identifies the author recognized worldwide.