C.S. Lewis’s childhood dog was named Jacksie, and its death inspired the nickname he used for himself. Lewis was born Clive Staples Lewis in Belfast in 1898, but as a child he rejected his given first name after the family dog was killed.
According to biographical accounts, the dog was struck by a car when Lewis was young. He subsequently asked to be called Jacksie, later shortened to “Jack.” The nickname remained with him throughout his adult life, and friends, colleagues, and family generally knew him as Jack Lewis rather than Clive.
The story is an important detail in Lewis’s early biography because it shows how personal experiences shaped the names by which he was known. “Jack” was not originally a literary pseudonym or an academic title. It was a private name that became his familiar identity in Oxford and Cambridge circles, including among the Inklings.