Jim points out
> Chambers Scots Dictionary gives Sandy Campbell as 'a pig'.

And that prompts me to look in The Scots Dialect Dictionary (Warrack, Waverley Books), where I find the same.

That and the link provided by Martin still leave unexplained why that particular name should apply.

Anyway, I need either to find a substitute, if I'm to sing the song in English, or to give up and sing it in Scots.

Richard