What is the origin of the idiom "part of the furniture" and when to use it?

The phrase "part of the furniture" originated in the early 20th century and referred to a person or thing that had been in a particular place or organization for so long that they were like a piece of furniture. The term "furniture" is used metaphorically to represent the idea of something that is permanent and immovable. It is often used in work or professional contexts, where someone may have worked for an organization for many years.