When Sanskrit and Avestan studies began in Europe in the late 18th century the word arya was noticed and came to be used for the family of languages we now call Indo-Iranian, i.e. most Indian, Iranian and European languages, and by extension, the people who spoke those languages. Europeans, particularly blue-eyed, blond-haired ‘Nordic’ peoples came to be seen as the ancestors of the ancient Aryans who had conquered India in ancient times, just as the British had conquered India (and half the rest of the world) in the 19th century. Thus the word took on a distinctly racist and imperialist coloring. By the late 19th century such an association was being discarded in scientific circles but among ill-informed people and especially among the more loony right-wing groups, particularly in Germany, it lingered. Hitler picked it up and the rest is history, very ugly history. As Nazism perverted everything it touched, it likewise gave the word arya/ariya something of a bad reputation. But of course, no informed person could find any similarity between how the word was (and sometimes still is) used by racists and how it is used in Buddhism. For all the uses of ariya in the Tipitaka have a look at the PTS’s Pali-English Dictionary and their new A Dictionary of Pali. The article ‘Arya’ in the Encyclopedia of Buddhism examines the use of the word within the wider Buddhist context and the article ‘Aryan’ on Wikipedia gives a pretty good account of the words use in philology and politics.
The Aryan race myth was never more effectively discredited than by those who loudly proclaimed it, not just in their behavior but even in their looks - Hitler with his sickly yellow skin and black hair, the grotesquely obese Goring, Dr. Gobbles with his club foot, cadaverous features and beak-like nose, the offish bald-headed Julius Streicher with his paunch, and the weakly, shortsighted Himmler. It’s hard to decide which of this bunch of Aryan supermen was the worst but if I was forced to choose I’d probably pick Julius Streicher. Even the other Nazis found him repulsive (although characteristically Hitler always liked him) and in 1940 he was quietly sacked and told not to attend any more Party functions. God! How unsavory would you have to be to be blackballed by the Nazis!
Related to this, the swastika, so often associated with the Nazis, has been used in Buddhism (and in nearly all cultures and religions) for centuries. Here is carvings incorporating swastikas on the Dharmik Stupa at Sarnath where the Buddha taught his first proclaimed the Dhamma.