Christopher Robin Milne’s childhood nickname was Billy, which combined with “Moon” to form “Billy Moon.”
“Moon” came from Christopher’s childhood mispronunciation of his surname, Milne. Within the family, he was therefore referred to as Billy Moon, although he later became more commonly known simply as Christopher.
Christopher Robin Milne was A. A. Milne’s only child and the real-life basis for the Christopher Robin character. His toys inspired several figures in the Pooh stories, while his visits to London Zoo helped connect his childhood world with the character of Winnie-the-Pooh.
The nickname is separate from the fictional character’s name. “Christopher Robin” was the name used in Milne’s books, whereas “Billy Moon” describes the author’s son in family life. Christopher later became an author and bookseller and wrote about his experiences of growing up connected with the stories.