Seems to me justice to this song would only be served in a line-by-line translation and i'm not up to that.

The bailie (numerous spellings) referred to is the cow-bailie, or man in charge of the cows. His loon is his boy helper.

Second and third denoted the rankings of the horsemen

Cathes door...? try 'cattle court'

Knappie knees...knobbly knees

Jack