IPA: /ˈbreɪkər/
KK: /ˈbreɪkər/
A person or thing that breaks something, or a device that interrupts a flow, such as electricity or water.
The circuit breaker stopped the electricity from flowing when there was a fault.
Breaker → It is formed from "break" (from Old English "brecan", meaning to shatter or destroy) and "-er" (meaning a person who). A breaker is a person or thing that breaks something.
Think of someone who 'shatters' or 'destroys' something — that's why a breaker is a person who breaks.