Taos lightning was a slang term for a straight Earth bourbon of dubious origin and low quality. After being injured by in a bar fight with Wyatt Earp, Doctor McCoy tended to Captain Kirk's wounds by dabbing them with Taos Lightning, much to Kirk's discomfort, referring to it as "fire." McCoy suggested the stuff to be "medicinal" in small amounts, to which Kirk replied that it should be labeled "for external use only."