C.S. Lewis's first name was Clive. He was born Clive Staples Lewis in Belfast, Ireland, on 29 November 1898. The initials “C.S.” became the name by which he was publicly known as a writer, scholar, and Christian apologist.
Lewis disliked the name Clive during childhood and was known to family and friends as “Jack.” He reportedly adopted that nickname after the death of a childhood dog named Jacksie. The name “Jack” remained with him throughout his life, including during his years at Oxford and Cambridge.
The middle name Staples came from his mother’s family. Lewis later became famous for The Chronicles of Narnia, literary criticism, and books such as Mere Christianity. His initials are sometimes mistakenly expanded as “Charles” or “Christopher,” but the standard biographical name is Clive Staples Lewis.