Hey Ron, Your Exxon question had me searching the web for the answer. I'm not sure if this is correct but found a site
http://uschamber.com with some info. Here it is:
Designing for Graphic Identity
Walk through any store and look at packages on the shelves. Decide which ones catch your eye in any given section, and why. Chances are the majority of packages that stand out have what's called "graphic identity."
Graphic identity is defined as a unique two- or three-dimensional graphic symbol that may be recognized by target buyers as being associated with a particular brand or business.
Sometimes this graphic identity takes the simple form of a unique brand logo or name with unusual letter shapes. For example, Exxon is an artificial computer-derived name without prior meaning. However, the unusual double XX in the name provides a unique graphic identity that makes this name recognizable even at distances where normal words are unreadable.