The origins of what is now known as the “Kit Kat” brand go back to 1911, when Rowntree’s, a confectionery company based in York in the United Kingdom, trademarked the terms “Kit Cat” and “Kit Kat”. Although the terms were not immediately utilised, the first conception of the Kit Kat appeared in the 1920s, when Rowntree launched a brand of boxed chocolates entitled “Kit Cat”. This continued into the 1930s, when Rowntree’s shifted focus and production onto its “Black Magic” and “Dairy Box” brands. With the promotion of alternative products the “Kit Cat” brand decreased and was eventually discontinued. The original four-finger bar was developed after a worker at Rowntree’s York Factory put a suggestion in a recommendation box for a snack that “a man could take to work in his pack”. The bar launched on 29 August 1935, under the title of “Rowntree’s Chocolate Crisp” (priced at 2d), and was sold in London and throughout Southern England.
Info gleaned from Wikipedia