What is the origin of the idiom "be on one's back" and when to use it?

The phrase "be on one's back" originated from the early 19th century and has its roots in the literal sense of someone physically being on another person's back. It evolved into a figurative expression to describe the experience of constant pressure, criticism, or demands from someone else. This expression can be applied in personal relationships, work environments, or any situation where someone feels overwhelmed by constant expectations or obligations.