I like to think of these versions as all relating to the same folk theme.
Here we have a theme of crossing a river which can be extended to include
such songs as 'Waters of Tyne' and even 'Running Bear'.

I suppose the theme must have been quite widespread in times when bridges were few and far between.

Hey Bill D. MY Dad used to say that as well so I suppose that saying itself is another piece of folklore.

And...
here - stuff - Polish Notation - that - start - don't:)

Bert.