Interesting Michael...
Of course in the ideal world, everyone would use the same terminology, particularly when it makes sense to be standardized. But then again you would be training in kilos, not pounds.
All kidding aside, in general, this is something that happens in every field when people give/apply a new meaning to a word, or perhaps a different usage and it becomes ambiguous in meaning. This is even more the case with field specific words...
I think that fitness has more "factors" that lead to this kind of thing. In particular, gym lore, and the word of mouth kind of teaching that goes on both from laymen and trainers, the lack of standards in the industry (in organizations/licensing/educat ion/certification), the "sell/marketing" aspect, the "macho" aspect and the ego aspect contribute to new namings. Some seem be quite appropriate and are appealing - to my mind, pistols, Arnold presses, skull crushers... though others like the Waterbury Walk, don't cut it for me- and are unlikely to catch on.
One thing you will find, is that you will not be able to "control" the language, some usages will catch on and like in other areas of language change they will become accepted names or usages.
Cheers
Peter