We had a workstation that would access a local tower or a mainframe... and you could toggle back and forth by hitting scroll lock, scroll lock, 2. The guy who set up the box pick scroll lock because it served no other purpose.
Actually, at one time the scroll lock key served a useful purpose when computers displays were slower than human reaction times. Under DOS one could print a file or directory listing to the screen. . . but if it was too long, a judicious use of the scroll lock key would interrupt the flow of data, stopping the screen from scrolling so the user could read the data before it scrolled up and outta sight. Another tap of the scroll lock key would resume the data flow and the scrolling, filling the screen with data until the next tap. Today, if you try that, the processor is so fast, the data fills far too fast for any human to stop it in any reasonable reaction time. It’s better to page the data.