What is the origin of the idiom "talk shop" and when to use it?

The origin of the idiom "talk shop" is unclear, but it likely dates back to at least the 19th century. The word "shop" here refers to a workplace or profession, and the phrase "talk shop" means to discuss work-related topics. It is typically used to describe a conversation that is focused on work-related topics, often between colleagues or people in the same profession.