Many people may think that the term derives from the from Proto Germanic word Swenganan, meaning "to fling oneself"... probably onto another person. While I can understand how some less educated people might make that connection, it is not the true origin of the term used by those in the swinging lifestyle.

Others believe that it derives from the German word Schwingen, meaning "to oscillate in a violent circulatory motion" I can only assume that a typical orgy situation involves a lot of oscillating violent circulatory motions... I wouldn't know since I've made a point of avoiding any and all social situations that I felt might have even the remotest chance of turning into an orgy. This includes hot tubs, office parties, group hugs, crowded elevators, crowded escalators, ferry boats, and any board games that require more than two people to play.

Getting back to your question, to understand the real origin of the term "swinger" one must look a the etymology of the word itself. "Swinger" is a compound word, comprised of two smaller words: SW and INGER. "S.W." is an acronym for "Shipping Weight" and "Inger" refers to "a member of western Finnish people formerly living in the Baltic province where Saint Petersburg was built."

In 1917 there was a mass migration of these western Finnish people from Russia. They didn't agree with Lenin's new communist government and decided to smuggle themselves into the United States inside a series of shipping containers. The voyage was long and tedious. But the western Finnish are a very resourceful people and had the foresight to bring plenty of fun board games along for everyone to pass the time... this inevitably led to a great number of orgies breaking out in these shipping containers. So that is how the shipping weight of a western Finnish orgy (or the "S.W." of "INGERS") became synonymous with today's modern perverts.