I found a very long discussion about it at letsrollforums.com - it's mainly a bunch of troofers deciding what the letters must stand for in order to prove an inside job. There was, however, one post towards the end which seemed to have some useful information. I haven't checked the veracity of it, but the post was made by someone who made the account, made this one post, and hasn't posted since, so I don't think it is a troofer source.
link to 13th page of the thread
Originally Posted by Beonoid @ letsrollforums
. Scroll 2/3 down for the post. The rest of the thread is junk.