Personally, first of all, I think this subject is right on topic, since the nomenclature for these parts has been consistent (or inconsistent) for many years.
Second of all, some axles DO rotate, note the rear axle on any front-wheel drive car.
Since, as far as I can tell, Sheldon Brown is, at least in part, responsible for this (if I may coin a really inelegant neologism) nomenclatural mayhem, I'll ask him: your reasoning is that axles spin, and things spin *around* a spindle, which is fixed...ergo, it's a bb *axle* and a hub *spindle*, right?
Not to put words in Sheldon's mouth, of course, and I'm sure he'll correct me if I have this wrong.
At any rate, this is, of course, exactly the opposite of the nomenclature I've used for the last 35 years.
And just to cloud matters in a perfectly charming fashion, here is the definition of an "axle" from my handy-dandy Webster's New World Dictionary: "a rod or spindle on or with which a wheel revolves." Note that under this definition the words axle and spindle are INTERCHANGABLE when referring to the parts under discussion! Even more charming, the definition of spindle from the same dictionary also uses the words axle *and* spindle interchangably....
All of which suggests to me that, at least from the point of view of the dictionary people, either word is good for either part.
I'm thinking I missed part of this...what do machinists and engineers call these parts, anyway?
Charles "spindle head" Andrews Los Angeles
PS: I will NEVER call that gear-shifting thingy on the back a derailer. Period.