K

Katie bar the door
8; The phrase "Katie bar the door!" (also as "Katie bar the gate!"; sometimes written as Katy) is a very American exclamation, more common in the South than elsewhere, meaning that disaster impends—“watch out”, “get ready for trouble” or “a desperate situation is at hand”. From WorldWideWords.org

Klu Klux Klan ("KKK")
7; the name of a number of past and present fraternal organizations in the United States that have advocated white supremacy, anti-Semitism, racism, anti-Catholicism, homophobia, and nativism. Wikipedia entry

Keeley Cure
17; a forerunner of certain measures adopted by Alcoholics Anonymous, the Keeley Cure was a system of treatment which relied heavily on injections of Bichloride of Gold (a chemical impossibility) was so well-known in its day, that several popular songs, such as an Irish comic song, entitled "The Keeley Cure," parodied it unmercifully. It was developed by American physician Leslie Keeley (1836-1900); Wikipedia entry