What was C.S. Lewis’s full first name at birth in Belfast in 1898?

C.S. Lewis’s first and middle names at birth were Clive Staples.

He was born on 29 November 1898 in Belfast, Ireland, to Albert James Lewis and Florence Augusta Hamilton Lewis. His initials came from these two given names, although “Staples” was also an important family name: his mother’s father was Thomas Hamilton, while “Staples” came from his father’s side of the family.

Lewis was commonly called “Jack” from childhood rather than Clive. The nickname reportedly arose after the death of his childhood dog, Jacksie, when Lewis began using “Jacksie” and later shortened it to Jack. “C.S. Lewis” became his public author name, especially after he began publishing poetry, apologetics, fiction, and literary criticism.

A common mix-up is assuming that C.S. stands for Charles Samuel or another conventional pair of names. It does not: the initials stand for Clive Staples. His full legal name is often given as Clive Staples Lewis, and his younger brother was Warren Hamilton Lewis.