'mainframe' originates from the combination of 'main' and 'frame', where 'main' meant 'primary' and 'frame' referred to the physical structure of the computer.

'mainframe' was coined in the mid-20th century to describe the central processing unit and main memory of a computer housed in a large frame.

Initially, it referred to the physical structure of the computer, but over time it evolved to mean the entire large-scale computer system.