What is the origin of the idiom "black hole" and when to use it?
The idiom "black hole" is derived from the astronomical term "black hole," which refers to an extremely dense region in space with such strong gravitational forces that nothing, not even light, can escape from it. In the figurative sense, "black hole" was later used to describe something that consumes vast amounts of resources, such as money, time, or effort, without yielding any productive or beneficial results.