It was written by Alex Glasgow, I believe. I have the words somewhere, but it begins

When Molly began to go courting,
Her mother was anxious to tell
How certain young fellas would want her
To stray down the pathway to Hell.
So Molly's old ma used to say:-

Keep yer 'and on yer ha'penny,
Cover it well with yer palm.
Keep yer 'and on yer ha'penny,
And Molly will come to no harm.