I served in the US Air Force for 20 years. Ever since I was 18, AF was always the abbreviation for Air Force.
So when "AF" suddenly entered the common lingo as "as fuck," it really threw me and my coworkers for a loop. Suddenly, everyone seemed to be talking about the Air Force, but the context didn't make any sense at all! It took a while before we learned that it meant something totally different.
... And then we felt old and out of touch.