تعریف و معنای "[catch] {sb} with {one's} pants down"

What is the origin of the idiom "catch someone with their pants down" and when to use it?

The phrase "catch someone with their pants down" is an idiomatic expression that is used to describe catching someone in a vulnerable or compromising situation, often when they are unprepared or engaged in an embarrassing act. The origin of this phrase is unclear, but it likely stems from the literal act of someone being found with their pants down, such as when they are caught in the middle of changing clothes or engaged in an inappropriate activity.