The article traces the evolution of the term 'mainframe' from its origins in 1952 with the IBM 701 computer, where it literally referred to the main physical frame holding computer components, through various meanings over decades. Initially used to describe the central processing unit or main box of any computer, the term evolved in the 1970s to specifically mean large, powerful computers, distinct from minicomputers and microcomputers. The word gained widespread use in the 1980s as personal computers became common, creating a need to distinguish larger systems.
https://www.righto.com/2025/02/origin-of-mainframe-term.html