Thanks a lot! I like that 1993 question from Ury Segal:

Where can I find an ftp which holds the Obfu. C context (sic) (the programs you can't read)?

Close, but no cigar because he uses "Obfu." (note the trailing ".") and it's not used as a noun.

I well remember after my first post here I got a couple of chatterbox messages saying "nice obfu" or "I liked your obfu". I remember thinking "what is this obfu business"? :)

In summary, I think the PM-meaning of obfu is more specific than simply an abbreviation of "obfuscated". Its canonical use, as in "that was a nice obfu!", is as a noun to describe an artistic composition of obfuscated code.