C.S. Lewis’s given names were Clive Staples. He was born Clive Staples Lewis in Belfast, Ireland, on 29 November 1898.
Lewis disliked the name Clive from childhood. After the death of his childhood dog, Jacksie, he adopted “Jack” as a personal name, and family and friends continued using it for much of his life. “Jack” was not his legal first name, while “C.S. Lewis” became the form used on his books.
The initials can cause confusion because readers sometimes assume the C stood for Charles or Christopher. It stood for Clive, and the S stood for Staples, a surname inherited from his mother’s family. Lewis’s brother was Warren Hamilton Lewis, usually called Warnie.
The author’s formal name is especially useful for distinguishing him from other twentieth-century writers and theologians. His books, including works of fiction, literary criticism, and Christian apologetics, were normally published under the initials C.S. Lewis rather than under Clive Staples Lewis in full.