What is plug nickel?

"Plug nickel" is a colloquial term used in the United States to describe something that is worthless or of poor quality. The origin of this term dates back to the mid-19th century when coins were made of silver and nickel. Counterfeiters used to make fake silver coins by plugging them with nickel. These fake coins had less value than the genuine ones, hence the term "plug nickel" came to signify something that is fake or useless. Today, the term is commonly used in everyday conversation to describe anything that isn't the real deal or is of low quality.