I just finished a book that was originally published in 1996, Bellwether by Connie Willis. It is, of course, a little dated since I'm reading it in 2010. The author used the term cellular phone instead of cell phone a few times which was a clear indication that some time had passed between her writing and my reading. It also left me wondering about words that were once abbreviations of longer versions.
There are company names. IBM, for example, was once International Business Machines and ITT was once International Telephone and Telegraph. Both of those companies are now officially known by their initials and, especially in the case of the latter, the work they do has little to do with their original name. Last I knew ITT was in businesses as diverse as hotels, technical education, and defense equipment.
I worked for a company a few years ago that made and sold lingerie. Every once in awhile we would get a nervous salesman who would explain how well the store fixtures they were selling would display the brassieres we were selling. I guess those guys used the formal term to avoid offending the women in our group, but instead the use of such an archaic term for bras left us all thinking we were dealing with people who had very little experience with our products.
There are also government organizations that are known by their abbreviations instead of their names. I suppose there was once a time when people referred to NATO as the North Atlantic Treaty Organization or when people knew what CARE stood for. Someone is bound to catch me on this. CARE isn't a government organization. It's an NGO, which is an example of an acronym that was, to the best of my knowledge, never known by its full name.
The point of all this is that language is always changing and can be tricky for writers, especially those of us who write historical fiction. But attention to this detail can be a great tool to make writing authentic.