Here's a marvelous explanation of the Irish "seven devils" as speculative superstition refracted by a mental prism into differently colored devils across the nations of the earth. From Holland-Tide or Irish Popular Tales
by Gerald Griffin, 1927. Favorite phrases: "If one were disposed to be fancifully metaphysical upon the subject ..." -- yes, one would be
so disposed! Ireland as a "step-daughter" island. And the zinger: "But what has this to do with the story? In order to answer that question, the story must be told."