"Moor," n.2, Oxford English Dictionary

"A native or inhabitant of ancient Mauretania, a region of North Africa corresponding to parts of present-day Morocco and Algeria. Later usually: a member of a Muslim people of mixed Berber and Arab descent inhabiting north-western Africa  (now mainly present-day Mauritania), who in the 8th century conquered Spain. In the Middle Ages, and as late as the 17th century, the Moors were widely supposed to be mostly black or very dark-skinned, although the existence of 'white Moors' was recognized. Thus the term was often used, even into the 20th century, with the sense of 'black person'."