Complex sentence: According to the 7th century writing of Isidore of Seville, the Latin word "Maurus" was derived from the Greek word for black, "mauron" (μαύρον), and at the time "Moors" were black by definition.
Split into simpler sentences: According to the 7th century writing of Isidore of Seville, the Latin word "Maurus" was derived from the Greek word for black, "mauron" (μαύρον). "In Isidore's day, Moors were black by definition..." During the time of Isidore of Seville, the Moors were considered to be "black people" by definition.