I knew Jimmy MacBeath and met him many times in the company of Hamish Henderson and Morris Blythman. Nigel Denver learnt the song from Jimmy's singing. I always assumed that blaw referred to what was gathered by itinerent people and ambiguously could mean stories as well as wheat/oatmeal and Jimmy always concurred when this was raised. Tod is the word for a fox not a toad and there are various Scottish folk songs which bear this out.