Some info on AMD's code names from the 'horse's mouth', as it were, over at AMDZone.

Postby JF-AMD on Sat Sep 26, 2009 4:09 am
Well you have to keep in mind that there are project code names, core code names, processor code names and platform code names.

Bulldozer is the project to overhaul the core. Orochi is a core. A modified orochi core will be in an Interlagos processor which fits in a Maranello platform. And there is an overall project name that I will not reveal.
While I work for AMD, my posts are my own opinions.

http://blogs.amd.com/work/author/jfruehe/
From JF's description, it appears that 'Zambezi' is the name for the desktop 32nm. If 'Orochi' is just a single core, as stated, the implication boggles the mind. Eight headed (threaded?) snake/dragon! I'm may be reading too much into the names - probably just a name without any hidden meaning.