What does the “xi” in 2605dnxi and 1100xi mean?

I was approached and asked about an HP Color LaserJet 2605dnxi and what exactly the “xi” means. I honestly didn’t know off hand but suspected that it had something to do with where the printer could be purchased (in this case it was Costco). First off, here’s a brief list of letters HP uses to describe the naming structure of its printers and what they mean.

D – Duplex (prints both sides of the page automatically)
N – Networking built-in to the printer
T – Extra tray included
MFP – Multifunction Printer (copy/fax/print/scan)
M – Retired term for Macintosh compatible printers
F – New letter that means fax machine included
X – Super Extended model with all the bells and whistles (tray, networking, toner)

So what does XI mean? Well from looking at a few forums and HP’s website I couldn’t really find much, but a printer with XI on the outside packaging generally comes with everything you need (like a USB or Ethernet cable), toner, support/warranty, etc. Here’s a list of possible meanings, although these are just guesses. Any suggestions appreciated in the comments.

XI – Extra Ink
XI – Extras Included