As far as I've looked into its origins, Frazer purposefully altered a huge amount of his data in various ways so that his conclusion fitted his hypothesis (that paganism had survived through Christianity in the form of folk customs). He suggested that folk customs were "cultural fossils". This is patently false, given a moment's consideration: folk customs are still evolving, even now. Whatever origin they may have in Paganism of any sort has been drastically hidden in layers upon layers of Christian overtones (and, at that, undertones).