What is the origin of the idiom "feather one's nest" and when to use it?

The idiom "feather one's nest" has its origins in the behavior of birds that use feathers, leaves, and other materials to build and line their nests for warmth and comfort. The idiom is used to describe individuals who prioritize their own interests, especially financial or personal gain, over the interests of others or the broader community. It suggests a focus on self-enrichment and a disregard for ethical considerations.