In the U.S., public restrooms go by various names—some call it the lavatory, others the restroom, and still others refer to it as “the throne.” One term, however, that remains a bit of a mystery for many is “WC,” often seen on restroom signs but not commonly understood.

Recently, this abbreviation caught the internet’s attention, leading to a flurry of comments. One person shared, “I’ve been wondering what it means for years but never googled it.” Another user chimed in with, “I can’t believe I’ve lived with a WC sign all my life and didn’t know what it stood for.” Some, on the other hand, were shocked that people didn’t already know. “What? Who doesn’t know this?” one person asked. While another stated, “Surely everyone knows what ‘WC’ stands for?”

So, what does “WC” mean? It’s an abbreviation for “water closet,” a term dating back to the early days of indoor plumbing. As indoor plumbing became more common in homes, people began converting small closet spaces into areas where toilets could be installed—hence the name “water closet.” Back then, bathrooms typically referred to spaces with bathtubs, not toilets. Over time, the term “WC” came to represent a toilet room, distinct from a full bathroom.

As one TikTok user explained, “Before indoor plumbing, bathtubs were in separate rooms, and water had to be carried in by bucket. When plumbing was introduced, the toilet was often placed in closets, leading to the term ‘water closet,’ or WC.” Today, the abbreviation is still widely used, especially in public restrooms, though many people remain unaware of its origins.