The traditional delivery model known as Waterfall was first shown diagrammatically by Dr Winston W. Royce when he captured what was happening in the industry in his paper, Managing the Development of Large Software Systems, Proceedings WesCon, IEEE CS Press,1970.
In it, he describes a gated process that moves in a linear sequence. Each step, such as requirements gathering, analysis or design, has to be completed before handover to the next step.
It was presented visually in Royce's paper in the following way:
The term Waterfall was coined because of the observation; just like a real waterfall, ...