"gang member, young ruffian," a transliteration of the Russian word for "friend," introduced by English novelist Anthony Burgess in "A Clockwork Orange" (1962). The Russian word comes from Old Church Slavonic drugu "companion, friend, other" (source of Bohemian drug "companion," Serbo-Croatian drugi "other"), which belongs to a group of related Indo-European words (e.g. Lithuanian draugas "friend, traveling companion;" Gothic driugan "do military service," ga-drauhts "soldier;" Old Norse drott, Old English dryht, Old High German truht "multitude, people, army") apparently with an original sense of "companion."
Examples from the Web for droog
The Droog was purple: not with the pellucid purple of a petal, but with the misty blue-black purple of the bloom of a plum.Of Walks and Walking Tours|Arnold Haultain