Very few folksongs need any 'insider' knowledge to write them, particularly rural songs.

And you can guarantee that any such insider knowledge would get lost in transmission. Only a small minority in any community know the exact sequence of operations involved in gutting a sheep, threading a loom or building a drystone wall, and if your song followed those steps in order, the next non-specialist to transmit the song would probably rearrange them in a sequence that couldn't actually work.