Folk magic, its practitioners and its records do not exist in a vacuum. The people writing down what we use as our primary source material on folk magic were not fussy about only writing down folk magic. They wrote down whatever they thought they might use, just as some of us do.
All that to say, even in folk magic primary sources, it's important to be cognizant of whether what you're reading has telltale signs of being from an external source and what other sources influenced the practitioners we study from, depending on the time of their writing.
