تعريف ومعنى "[wait] in the wings"

What is the origin of the idiom "put someone out to pasture" and when to use it?

The idiom "put someone out to pasture" is believed to have originated in the United States in the early 20th century. It refers to the practice of retiring old or worn-out farm animals and allowing them to graze in a pasture. This idiomatic expression is used to describe a situation where someone is forced to retire or is no longer useful or productive in their job.