David Herd, Ancient and Modern Scottish Songs, Heroic Ballads, etc. In two volumes, 1776, Vol 2, page 205:

"Cock up your Beaver"

When first my dear Johny came to this town,
he had a blue bonnet, it wanted the crown;
but now he has gotten a hat and a feather,
Hey, my Johny lad, cock up your beaver.
Cock up your beaver, cock up your beaver,
Hey, my Johny lad, cock up your beaver;
cock up your beaver, and cock it nae wrong,
we'll a' to England ere it be lang.

I like this pre-Burns version. I think Burns's modification of this is good, too.

T.