the word itself is not unusual, but its origin is interesting. It derives from the Old French word gargouille, which means throat.
1. A grotesque spout, representing some animal or human figure, projecting from the gutter of a building (esp. in Gothic architecture), in order to carry the rain-water clear of the walls.
(definition courtesy of Oxford English Dictionary online)
and of course, some of the most spectacular examples can be found at notre dame de paris, where the gargoyles are used for both drain pipes and decoration.