Arthur John became initialized early in life. Initialization is a Southern rite of passage akin to the Hebrew practice of circumcision, but it is sometimes less painful and does not always occur on the seventh day. So Arthur John Longstreet became A.J., and A.J. he has remained.
This is from The Front Porch Prophet by Raymond L. (R.L.?) Atkins, a book I somehow got a free copy of for my Nook. Not sure anything about it or if I'll enjoy it--this isn't a recommendation or review or anything--but just reading the opening, I came across that line and liked it.