C.S. Lewis’s first name was Clive. His full birth name was Clive Staples Lewis, although he was widely known by his initials and later acquired the nickname “Jack.”
Lewis was born in Belfast, Ireland, in 1898. “Staples” was his mother’s surname before marriage, and it became his middle name. The initials “C.S.” therefore stand for Clive Staples, not Charles Samuel or another commonly guessed combination.
During his school years, Lewis began calling himself “Jacksie,” after a childhood dog named Jacksie. The nickname eventually shortened to “Jack,” and friends and colleagues generally used that name. His published works, however, appeared under the name C.S. Lewis.
Lewis became a literary scholar, Christian writer, and novelist. His best-known works include The Chronicles of Narnia, Mere Christianity, and The Screwtape Letters. The contrast between his formal initials and informal nickname is one of the most recognizable details of his biography.