Earther or Earthling was a derogatory term that was used in reference to Humans in the 23rd and 24th centuries. (ST reference: Federation Passport) The term was most commonly used by the Klingons in the 2260s as tensions between the Federation and the Klingon Empire were at their highest. (TOS novel: The Edge of the Sword; TOS episode: "The Trouble with Tribbles") In 2372, a Bajoran customer in Quark's called Miles O'Brien an Earther, angering him. Quark diffused the situation by saying O'Brien had killed two Caxtonians after they angered him. (DS9 novel: The Heart of the Warrior)