DebC's story about the Folk festival insisting on original material is fascinating. their cant be many examples of words changing their meaning to their own opposite in one generation. Other musical genre terms have changing meaning hugely, but at least a lot of jazz still sounds jazzy, and a modicum of modern rhythm'n'blues still sounds rhythmic and bluesy. But DebC's example is amazing, where songs that were defined as folk (or the songs that defined folk, to be more precise) in 1960 cannot be sung in a folk festival competition 40 years later.