Thanks for the link Pseu'.

Jim. Before universal primary education kids were employed, or doing something practical and useful around the house or farm, from an early age. They would grow up knowing the technical terms for the work they and their family members did. Layock's life illustrates how someone writing songs can know the technical terms for a trade without being employed in it for more than few years. Like him, those who learned to read and write might get a 'lift in the world'. We don't know how many of the folk who wrote songs really were illiterate.