Vicious circle originally referred to a circular argument, that is, an argument that assumes the conclusion as one of its premises. That sense was first documented around the end of the 18th century. Approximately 50 years later, vicious circle acquired the now more common "chain of events" sense as people began to think of the circle as a metaphorical circle rather than a circular argument. Today, vicious cycle is a common variant for the "chain of events" sense. Vicious spiral, in which the ill effects are cumulative as well as self-aggravating, puts in an occasional appearance as well.