Many people are just now discovering that “WC” on toilet signs stands for “water closet.” The term dates back to the early 1900s when homes first installed indoor plumbing and toilets were often placed in small closet-like rooms. As the article explains, these spaces had “one of the few sources of running water in the house,” earning the name water closet.

Today, we commonly say “bathroom,” but historically, that referred only to a room with a bathtub. A water closet, by contrast, was a small room with just a toilet.

Though language has evolved, “WC” is still widely used, especially in Europe, to mark a toilet-only restroom. It’s a reminder of how older plumbing designs still shape modern terms.