AppleInsider notes that it appears to be related to the PastryKit framework used for the iPhone user-guide (which stands to reason), and the TuneKit framework used for iTunes LP and iTunes Extra. And that the name may tie-in to the iAd rumors, and to internal efforts on Apple's part to raise the bar of web apps and diminish the need for plugins like Flash and Java.
Could we find out more at Apple's iPhone 4.0 event tomorrow? We certainly hope so. As much as some decry the closed nature of the App Store, developing for Safari is wide open and a new class of better, faster, stronger web apps is ultimately good for everyone.
Video after the break!