Which 19th century British physician discovered the condition and coined the term, Mongolism (which is currently considered ethnically offensive today)?

In 1866, the British physician John Langdon Down published a highly influential paper that provided the first comprehensive description of the condition now known as Down syndrome. Working as the medical superintendent at the Earlswood Asylum in Surrey, he observed that a distinct group of his patients shared a common set of physical characteristics, allowing him to classify their condition as a separate and recognizable disability.

Down's work was shaped by the prevailing, and now-discredited, anthropological theories of the 19th century. He incorrectly theorized that various developmental conditions were a kind of ethnic regression. Based on his perception of a facial resemblance between his patients and people of East Asian descent, specifically Blumenbach's "Mongolian race," he coined the term "Mongolism" for the condition. This ethnically-based classification has since been proven to be scientifically baseless.

While his theory about its origins was wrong, Down was a progressive figure for his era, advocating for the education and humane treatment of people with intellectual disabilities. In the 1960s, a group of genetic experts, along with a formal request from the Mongolian People's Republic, successfully petitioned the World Health Organization to change the name. The condition was officially renamed Down syndrome to honor its original discoverer while permanently discarding the offensive and inaccurate terminology.