by the end of the 20th century, the name "disco ball" had largely eclipsed the earlier names that had been applied to, for example, the one that can be seen in the 1942 movie Casablanca.
"National Products Inc. has manufactured disco balls and lighting effect products for professional sports arenas, theatrical shows, trade shows and nightclubs for over 50 years."
The first effects lighting appeared long before disco's started. Before the war it was discovered that if you shine a light on a ball covered with mirrors that you get one beam off every mirror. My earliest recollection of a mirror ball was in the 1942 film Casablanca, with Humpfrey Bogart.
Its popularity reached its peak in the mid-1930's big band era. Glenn Miller, Tommy Dorsey, and others, headlined the ballroom. Though liquor was prohibited and the dress code strict, thousands jammed onto the dance floor and danced beneath the large, mirrored ball.