Testimony of Tradition by David MacRitchie

From the author of Ancient and Modern Britons David MacRitchie explored numerous traditional, legendary, and contemporary accounts dealing with mound-dwelling, elfin types, who served as a basis for the mythologic fairies, leprecauns,brownies, etc. MacRitchie concluded that they were based on Twas or Twas mixtures of people.

This is another gem worth reading.