The term refers more to the set of instruments than to the players of those instruments. A gamelan is a set of instruments as a distinct entity, built and tuned to stay together — instruments from different gamelan are generally not interchangeable.
The word "gamelan" comes from the Javanese word "gamels", meaning to strike or hammer, and the suffix "an", which makes the root a collective noun. Real hammers are not used to play these instruments as heavy iron hammers would break the delicate instruments.
Source : http://en.wikipedia.org/wiki/Gamelan
