1867, American English, originally Kuklux Klan, a made-up name, supposedly from Greek kuklos, kyklos "circle" (see cycle (n.)) + English clan. Originally an organization of former Confederate officers and soldiers, it was put down by the U.S. military in the 1870s. Revived 1915 as a national racist Protestant fraternal organization, it grew to prominence but fractured in the 1930s. It had a smaller national revival 1950s as an anti-civil rights group, later with anti-government leanings. In late 19c. often simply Kuklux.
<a href="https://www.etymonline.com/word/kluxer">Etymology of kluxer by etymonline</a>
Harper, D. (n.d.). Etymology of kluxer. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/kluxer