Donald Gilles, who worked at the JWT London advertising agency in May 1957, is credited with coming up with the Kit Kat slogan "Have a Break." Break has two meanings, making it the ideal name for the product. "Break" is used to rest as well as to break the bar (alluding to the distinctive sound that is made when you do so). With "Have a Break," this dual meaning would serve as the slogan's mainstay.

It started appearing in the company's first television advertising a year later. It has since been a mainstay in Kit Kat's advertising campaigns. As the tagline took shape, designers discovered that the idea was incredibly flexible. All kinds of amusing, frustrating, and humorous circumstances could benefit from taking a break.

The endurance of "Have a Break" was largely due to its adaptability. Donald Gilles was able to do what other businesses needed years to do, such as Nike with "Just Do It" or Adidas with "Impossible is Nothing," because to the term "Break's" dual meaning. Unknowingly, they created an idea in 1957 that was so influential that it served as the basis for modern marketing. It represented a before and after in the vernacular of advertising and a choice that the customer was "forced" to make because of the goods. "Have a Break," take a break from all you're doing and the outside world, and take some time just for you.