/u/jan_van_bergen has previously written about Why did Hitler specifically choose to call his desired race "Aryans" rather than "Nordic" or "Germanic"?
/u/killfile has previously answered Why was being Aryan such a big deal to the Germans?
EDIT: /u/Georgy_K_Zhukov has previously answered How did "Aryan" come to mean blonde haired blue eyed white supremacists when the Aryan people were part of the ancient Vedic culture, who by geography would not have been white or blonde?