Its really interesting, that many people find confused about, who coined the concept of PDCA, is it Deming or Shewhart?
The basic idea began with Shewhart's attempt to understand the nature of knowledge.
Shewhart believed that knowledge begins and ends with experimental data, but it doesn't end in the data in which it begins.
Since knowledge begins with original data and ends in new data, these future data constitutes the operationally verifiable meaning of the original data.
This Idea seeded the concept of the model in the mind of Shewhart which is known as: specification➡Production➡Inspection
The model is called scientific process of acquiring knowledge.
Later on, Shewhart and Deming revised this model for application to the improvement of product and processes.
This new model was first called PDCA cycle i.e. Plan-Do-Check-Act, but Deming revised it and replace the word "Check" by "Study" as it reflects more clear meaning of the model.