THE BLACK MAN IS THE BLUE MAN A Middle English word for “Ethiopian” (perhaps also “a negro” generally) was blewman “blue man” “Varying shades caused those natives to be styled by their Latin conquerors — sometimes Virides, or Green-men — and sometimes Cærulei, or Blue-skins” “The colour of the people whom Caesar styled green-men and blue-skins is described by Pliny as Æthiopium (as black as a “blackamoor’s”)” “What is Duine-Dubh, “a black man” in one part of the country, is Duine-Gorm, “a blue-green man” in another” “And as the Gaelic word for “a wild Irishman” signifies literally “a Black-Irishman”, and as it is in Ireland that “a black man” is “a blue-green man”, it may be assumed that most—or all—of the wild tribes of Ireland were blue-skins or green-men, also during an undefinable period” SOURCE;
(Ancient & Modern Britons; 1884)