This is the first version of Android that's under a brand name. Previous code names for the OS platform (which usually are desserts) were Cupcake, Donut, Eclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwich and Jelly Bean.
The release had long been expected to be numbered 5.0 and called 'Key Lime Pie'. (text source: Wikipedia)