By what other name were the righteous fists of harmony known?

They were known as Yihequan or Boxers.

The Righteous and Harmonious Fists was a name foreigners gave to Chinese secret society that precised certain boxing and calisthenic rituals. They were well trained athletes, their primary practice was a type of spiritual possession which they thought made them invulnerable. They were armed with swords and rifles, and they believed that millions of soldiers of Heaven would descend to assist them in order to purify China from the influx of foreigners.

The Boxer Rebellion was an anti-foreign and anti-Christian upraising that took place in China between 1899 and 1901.

The name Boxers was given to them by American Christian missionaries because of the martial arts and weapons training they practiced.