Question: why is a 99 called that?
Answer: One claim is that it was coined in Portobello, Scotland, where Stefano Arcari—who had opened a shop in 1922 at 99 Portobello High Street—would break a large "Flake" in half and stick it in an ice cream. ... The Cadbury website says that the reason behind the Flake being called a "99" has been "lost in the mists of time".