"I was exploring what Child meant by "popular", if he did not mean "Produced by the common people"."
"Popular" means of the people - or did did before the advent of 'the charts'
Whatever society Child envisaged, the fact is that one of the main sources of the ballads were the Unlettered Travelling people and the rural working classes - the 'lower ends' of society
The same with the tales - the comparisons with stories from a living or recent tradition and the ballads become obvious
Jim