First off, I'm surpised nobody has mentioned Bob Dylans "I Pity The Poor Immigrant," from the John Wesley Hardin album. It's a straight lift.

Secondly, the verse about the "Clyde" was written by the late Jim Reid, who is famous for writing "Norland Winds/Wild Geese. The last line about the county of Angus, where Jim lived, is a dead giveaway.

"Bla" as far as I've always understood it was the wool left by sheep on fences, etc which was gathered up and sold. It's not a word used a lot these days, but if I remember, I'll ask some of my older relatives. I've also heard this line sang as, "gie yer airs a bla." Many travellers played the bagpipes, and "airs" are tunes.

Jimmy McBeath may have lived in Ireland for a time, but it's well known in Scottish folk circles that he was given his version of "Tramps and Hawkers" by George Robertson Stewart, a settled traveller and businessman from Huntly in Aberdeenshire. He(Big Geordie)always said HE wrote it.

Finally, for our American and English cousins, the name McKay, is pronounced Mac-Eye, not Mac-kay.