The decision to brand the software with the name of Nestle's chocolate bar is likely to be seen as a marketing coup for the Swiss food and beverage maker, which plans to sell more than 50 million KitKat bars displaying the green Android mascot.
Google officials said they had originated the idea, which did not involve any financial arrangement between it and Nestle.
"This is not a money-changing-hands kind of deal," John Lagerling, director of Android global partnerships, told the BBC.
The idea, he said, was to do something "fun and unexpected."
"We realized that very few people actually know the taste of a key lime pie," he explained.
Consumers around the world are familiar with the KitKat bar and generally will have positive associations with that name, although such branding exercises are not without risks, one analyst said.
If one of these two brands involved has a recall or scandal it can taint the other, Allyson Stewart-Allen of International Marketing Partners said.
A Nestle executive acknowledged that, saying for example if the new OS proved to be crash-prone or particularly vulnerable to malware it could cause collateral damage to KitKat's brand.
"When you try to lead a new way of communicating and profiling a brand you always have a higher risk than doing something much more traditional," Nestle marketing head Patrice Bula said.