Here's what I found - accredited as "old traditional"

FISH AND TIN AND COPPER

Old Nick as he was wont to do
Was wanderin' up and down
To see what mischief he could brew
And made for Launceston-town.

(chorus)
For 'tis fish and tin and copper, boys,
(Three ?placenames? Tre- ?, ?, Pen-?)
One and All, we may rejoice
That we are Cornishmen.


Across the Tamar he had come.
Now you might think it strange.
And having left his Devon home,
Tried Cornwall for a change.

(chorus)

Now when to Launceston he drew near
A-skippin' o'er the sod,
He spied a rustic cottage there
With windows all a-broad.

(chorus)

And in the kitchen might be seen
A dame with knife in hand
To cut and slash and chop I ween
To make a pasty grand.

(chorus)

"Good Mornin', Missus, what is that?"
"Of all sorts, it is then.
'Tis beef and mutton, pork and fat,
Potatoes, leeks, and squab."

(chorus)

"A Cornish pasty, sure", says she,
"And if thou doesn't mind,
I soon shall start to cut up thee
And put ye in, you'll find!"

(chorus)

In fear he turned and straight did flee
Across the Tamar green
And since that day in Cornwall
He has never more been seen!

(chorus)