The Cheshire cat was a character in the book Alice's Adventures in Wonderland, by human author Lewis Carroll, an anthropomorphic cat encountered by Alice. The Cheshire cat was distinguished by its smile, which would remain visible even after the rest of the cat had disappeared.
History and specifics
Seven-year-old Robin Lefler adopted the nickname "Cheshire" (or "Ches") after reading Carroll's books with her mother, Morgan (who took the nickname "Alice"). (NF short story: "Lefler's Logs", "Alice, on the Edge of Night")