No need to call in the straight dope: I gots your etymology right here:
From the Greek akros, meaning "extreme" and onuma, meaning "name". cf. synonym, antonym, etc. etc.
So, what we're dealing with here is an "extreme name", which I think is kind of nice. Instead of just picking a random name for something, you go to the extreme lengths of trying to make the initials of a descriptive sentence form a pronouncable word. Very much in the spirit of extreme sports.
Sorry to disappoint those of you who were hoping that the word was in itself an acronym. And while we're on the subject, there is no Santa Claus, and fuck is not an acronym of "For Unlawful Carnal Knowledge". Sorry.
Some info gleaned from The American Heritage Dictionary of the English Language, Third Edition. Copyright © 1996, 1992 by Houghton Mifflin Company.