The term mottled enamel to Colorado stain was given by:
The history of fluoridation started with the arrival of Dr. Fredrick McKay in Colorado Springs, Colorado, USA, in 1901, the year following his graduation from the University of Pennsylvania Dental School. He noticed that many of his patients, particularly those who had lived in the area all their lives, had an apparently permanent stain on their teeth, which was known to the local inhabitants as ‘Colorado Stain'. 
McKay checked the notes he had saved from dental school but found nothing to describe such markings, nor could he find any reference to them in any of the available scientific literature. He called the stain 'mottled enamel' and said that it was characterized by minute white flecks or yellow or brown spots or areas, scattered irregularly or streaked over the surface of a tooth or it may be a condition where the entire tooth surface is of a dead paper-white like the color of a china dish.
Essentials of preventive and community dentistry
Soben Peter
5th edition
 page no. 252
McKay
Black
Dean
Jones