I hate to say this but, just because it's the Copper Family, it doesn't mean it's 'traditional' (except to the Copper Family perhaps)!

When I researched Dame Durden as part of the Millen Family repertoire (which was slightly different), I found a printed version from the 1830s. In fact, the Millens' version is more or less the same as that sang by The Mellstock Band on one of their CDs displaying the vocal diversity of the soloists rather than the unison version the Coppers do. Someone out there is bound to insist it's one of Henry Purcell's cleaner glees popular in 17th century coffee houses.

Other Copper songs that springs to mind as having slightly different versions elsewhere include Corduroy and Twankydillo. IO daresay there are others.