It's the most unlikely suggestion so far (because of linguistic usage), but that doesn't necessarily mean it's wrong.

I am likely totally wrong, but the reason I suggested it is that the context makes it possible.

"ablaw" and "oblaw" are mentioned in previous posts, but equally, given oral transmission, why not "o' blaw"? Maybe "blether" was a bit tenuous, but "blaw blaw blaw..." is often used as a term for incessant chatter.

Before the advent of radio and TV and in a era of less than 100% literacy, the various itinerant travellers were important as purveyors of news - especially of tittle tattle. Who was born or died or married, who had given birth, local scandal, the small doings of the celebrities of the day. In fact in many ways they fulfilled the role that the tabloid newspapers fill in todays society.

In that context, interpreting the first line as I did makes, to me, perfect sense.

Incidentally, the recording I have is by Robin Hall and Jimmy MacGregor who made a couple of very good albums of traditional Scottish songs in the mid 60's