[RupertSalt]

A disc jockey is an entertainer who spins records or compact discs to play music.

A discothèque is a nightclub where disc jockeys can perform live, spinning to create a party atmosphere for socializing and dancing.

In the United States, the word was quickly shortened to "disco" and became closely associated with the mirror ball on the ceiling and the eponymous style of music and dancing.

So when new styles of music overtook the nightclubs, they shed the "disco" appellation as well. It seems to still enjoy a lot of use in European cities, though.