A question for any 'old' (OR 'New') Folkies - Any songs you first heard introduced as traditional that turned out to be recently written ?

I recall hearing 'Dark as a Dungeon' introduced as "An English Miners song from the early eighteenth century" with NO mention of its actual American contemporary origins .

I know that Keith Marsden himself used to introduce 'Bring us a Barrel' as trad in his early days - Any other examples people can think of ?