Swing dancers are often referred to as jitterbugs because they dance without any control like an alcoholic who suffers from the ‘jitters’. It can also mean a type of Swing dance or the act of Swing dancing. In 1934, Cab Calloway recorded Call of the Jitter Bug and the film Cab Calloway’s Jitterbug Party which popularised the word.
Original caption: 9/23/39-New York: Alfred Schock and Evelyn Stein are going to town in a big way during the jitterbug session that marked the opening of the Mardi Gras swing casino at the New York World's Fair. The casino is free to all fair goers -- all rug-cutting is strictly on the house.