I think it is because Jim Gettys coined the term very recently. It seems likely that he is the very first person to discover this phenomenon.

Although there is a small chance that someone else also discovered it independently but came up with their own phrase to describe it -- a word that does not show up when you search for "bufferbloat".

The word "bufferbloat" is OK but it is not quite on target, imho. I don't have a better suggestion, but I think a better alternative is out there somewhere. Such a word would convey, not just the notion of bloatage, but also the notion of bits getting stuck in the comfortable expanse of modern, obese, buffers, fed at a rapid rate by modern hardware (and TCP stacks) on clean pipes.

Grasping at metaphors, I'm thinking of dampeners like bit potholes, quicksand, flypaper, speed bumps, bit tarpits...