You are not going to get an answer to this unless Google decides to reveal it one day. To quote this article
Google doesn't want to explain.
"It's kind of like an internal team thing, and we prefer to be a
little bit -- how should I say -- a bit inscrutable in the matter,
I'll say," said Randall Sarafa, a Google spokesman. "The obvious thing
is that, yeah, the Android platform releases, they go by dessert names
and by alphabetical order for the most part." "For the most part"
because two versions of Android, 2.0 and 2.1, were both called Eclair.
And because Google won't say what it called the first two versions of
Android, which you can assume started with "A" and "B." "As far as the
public knows, it started with Cupcake," Sarafa said
This is also an interesting article on the names used on Google's operating systems
There might also be a demographic reason behind the name of the sweet chosen to. To quote this article
Podhajsky said that Kit Kat's jingle is a good fit for people taking a
break to look at their smartphones or tablets. She added that the deal
appeals to Hershey because Android hits the sweet spot of Kit Kat
eaters, who are typically between the ages of 18 and 34.
"Kit Kat consumers are young, vibrant consumers of candy and chocolate
bars, and that's a nice match with Android," Podhajsky said.
However it could just be a matter of personal preference as well
The Kit Kat name was unexpected since tech pundits have speculated for
months that the next operating system would be called Key Lime Pie.
Marc Vanlerberghe, director of Android Marketing, said the name was
chosen because Kit Kat bars have been a "favorite go-to snack among
the team since the early days of Android."