https://www.google.com/search?q=the+discover+of+refactoring+code+in+1990s&rlz=1C5CHFA_enUS1047US1048&oq=the+discover+of+refactoring+code+in+1990s&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIJCAEQIRgKGKABMgkIAhAhGAoYoAEyCQgDECEYChigATIJCAQQIRgKGKABMgkIBRAhGAoYoAHSAQkxMDIzMWowajeoAgCwAgA&sourceid=chrome&ie=UTF-8 QT:{{” Refactoring code wasn’t “discovered” in the 1990s but was formally defined and popularized then, with Bill Opdyke and Ralph Johnson coining the term in 1990 and Opdyke’s 1992 dissertation detailing it for OO systems; later, Martin Fowler’s 1999 book, Refactoring, solidified the practice, linking it with Extreme Programming (XP) and automated tools for cleaner, more maintainable code. “}}