It came from the 70s: Hanging Disco Ball
Few things in life define the mood better than a hanging disco ball.
Whenever most of us see one, we think 70s disco fever. You know,
leisure suits, bell bottoms, platform shoes, hips swaying, porn
mustache, Afro hairstyle, open shirts displaying a hairy chest with
large gold medallion, permed hair, body sparkles, facial glitter, and
pretty much anything you see in night clubs in the 70s. Not to mention
the sounds of Bee Gees, Donna Summer, Earth Wind & Fire, Gloria
Gaynor, Abba, and other legendary musicians.
For those of use not old enough, we can only think of the Saturday Night Fever poster with John Travolta in white leisure suit and his dance partner in red flowing dress on a colorful dance floor with a hanging disco ball on the ceiling. Hey, it's still disco.
But also, there are constantly plenty of disco-themed parties attended by the younger generation and these parties mimic the atmosphere of 70s disco. And they all have a mirrored disco balll hanging in the center of the dance floor. It rotates and reflects back colorful moving lights on the walls. You can't help but be in the mood to dance the night away. Danceable, melodic disco tunes help, too.
Curiously enough, however, the disco ball has been around long before the 1970s. Wikipedia dates it all the way back to The Roaring 20s when Jazz was the mainstream music for young people. And I'm quite sure that the hanging disco ball was there to help setup the party mood as well.