C.S. Lewis’s first given name was Clive.
He was born Clive Staples Lewis in Belfast on 29 November 1898. “C.S.” came from his first two initials, while “Lewis” was his family surname. The middle name Staples honored his mother’s family, which had connections to the Staples family of County Down.
Lewis disliked the name Clive from childhood and adopted the nickname “Jacksie” after a childhood dog was killed. The nickname was later shortened to “Jack,” the name used by friends and family for the rest of his life. He is therefore commonly identified as C.S. Lewis or Jack Lewis rather than by his first name.
A common mix-up is assuming that “C.S.” stands for Charles Staples. It does not: the initials are Clive Staples. Lewis later became one of the twentieth century’s best-known Christian writers and children’s authors.