Statistical process control (SPC), as you probably know, is an industry-standard methodology for measuring and controlling quality during the manufacturing process. The concept was developed at Bell Laboratories in the 1920s by physicist and statistician Walter A. Shewhart, who came to be known as the father of statistical quality control.
Shewhart realized that he could detect differences in the sources of variation of a manufacturing process—whether sources were “common” (natural/predictable) or “special” (unusual/unexpected). He described common variations as “in control” and special variations as “not in control.” And thus, the control chart and SPC were born.