What is the origin of the idiom "be better off" and when to use it?

The origin of this idiom is believed to date back to the 16th century, when it was first used in the sense of "to have a better condition of life." The phrase "off" in this context means "away or distant from a previous or less desirable situation." So, to be "better off" meant that one was farther away from a previous, less desirable situation and closer to a new, more desirable situation. It is now commonly used to refer to any situation in which someone has improved their condition or situation, whether through their own efforts or through external circumstances.