Personally I think if people have to look up the term then you’ve already lost them. Looking at the synonyms for "lexicon" (
http://thesaurus.reference.com/browse/lexicon) there are plenty of other terms that might be more obvious. Here’s some examples:
dictionary, glossary, language, vocabulary, dialect, jargon, lingo, terminology, wordbook
"wordbook" is a pretty good one. Can’t get any more obvious than that. Think of it in terms of how you would describe a file for a specific language. You could tell someone to look in the German "lexicon" file or the German "wordbook" file. Which terms would the average "junior" web developer catch on to more easily?
The other two terms I like are "jargon" and "lingo". Those are just as obvious if not more obvious. They imply that they are more than just simple dictionaries.
The thing is that we can’t ignore the young web developers that are just starting out. As such, the terminology we use to describe the elements of MODx needs to use real world language in my opinion. From an information design perspective, this is far more important than you realize because the terminology you use has an impact on how someone new to the platform will relate to it. We really need to evaluate our core audience and realize that not all developers think alike. A good number of them will be new and may not gravitate to the concepts in the same way if they don’t understand the lingo. Let’s help them by gearing the lingo to match terms that are easily comprehensible to just about anyone.