Term started way back when we first decided to add the extra on there... In the "good ole' days" you had no gauge, just flip the J valve when it got hard to breathe, no octo - love buddy breathing, and no inflator hose... Didn't have BCs. Weight yourself right and control with air in your lungs, not a vest...
Well, these items started appearing adding another hose and another, and the last to be added was the spare reg... and someone once said, "With all those damn hoses hanging down it looks like a darn octopus" and the name just stuck... onto the last hose added, the backup 2nd stage... the octo.
(oops.. just went and read the article that was linked in previous post.... kinda said the same thing I did... Well at least good to know I was right! Sorry for the reduncancy, redundancy, redundancy.)
But why is it "occy" for people overseas??