"[keep] up appearances" の定義と意味

What is the origin of the idiom "keep up appearances" and when to use it?

The idiom "keep up appearances" originated from the notion of maintaining a certain outward image or perception, often to conceal or disguise one's true circumstances, feelings, or intentions. The phrase signifies the act of presenting oneself or one's surroundings in a manner that upholds a desired impression or societal expectations, regardless of the underlying reality. This expression is commonly used to describe situations where individuals or groups make efforts to appear a certain way externally, even if it contradicts their internal state or actual circumstances.