the.com/switchover

means The act of changing completely from one system, method, or thing to another.

from A straightforward 20th-century compound of 'switch' (to change or shift, from the sense of the lever or device that redirects electrical current or railway tracks) plus 'over' (indicating completion or transition). It emerged alongside the language of engineering and broadcasting, where throwing a switch could reroute a circuit, a train, or a signal — so the word carries a faint hum of machinery even when it's just your office changing payroll software.