What is the origin of the idiom "filthy rich" and when to use it?

The idiom "filthy rich" likely originated in the United States in the early 20th century. The term "filthy" is used in this context as an intensifier, emphasizing the excessive or overwhelming amount of wealth possessed by someone. It is used to describe someone who is extremely wealthy, often to the point of being considered excessively or outrageously rich.