Best explanation from
whatapain from The Hive:
http://mbd.scout.com/mb.aspx?s=140#s=140&f=2938&t=1763365&p=2
GoldenTornado wrote: B-Back has to be a recruiting thing. Navy did not use the term. It's definitely a great pun on Bee and I bet that was part of the reason.
But calling the position a "fullback" is misleading because the position is really a big tailback who can easily get 25 carries per game, and at this level that could be used against us.
I googled and apparently it comes from calling the three backs A-B-C, where the slotbacks are A and C, in the same way that the LB's are called Sam-Mike-Willie.
It is not a recruiting thing. The A backs are the slots & the B back is the fullback. This is the terminology used. Yes, the A's can be called slots and the B's fullbacks but don't say it's for recruiting. I've been around the offense for 18 years (give or take) and they've always referred to the players by A's or B's. You'll be hearing from me "the A's make the plays" a lot during the season. Their ability to block, run & receive make them the most diverse & exciting group in the offense. Don't get me wrong, the QB is key and the B back will get a load of carries but the A's will be the guys breaking off the big gainers to the perimeter.