OGNL stands for Object-Graph Navigation Language; it is an expression language for getting and setting properties of Java objects. You use the same expression for both getting and setting the value of a property.
OGNL started out as a way to set up associations between UI components and controllers using property names. As the desire for more complicated associations grew, Drew Davidson created what he called KVCL, for Key-Value Coding Language, egged on by Luke Blanshard. Luke then reimplemented the language using ANTLR, came up with the new name, and, egged on by Drew, filled it out to its current state.
We pronounce OGNL as a word, like the last syllables of a drunken pronunciation of "orthogonal" or like "ogg-null".