Anyone have any idea on how old the tune is? It was certainly well enough known in the early 1700s to be widely parodied; it showed up in the French and Indian War, it was used in The Beggar's Opera (1728). And it was at least referred to in Mother Goose:
Tom, Tom, the piper's son
Stole a pig and away he run
The only tune that he could play
Was "Over the hills and far away".