WC means Water Closet. Yes, it’s that simple. The term dates back to Victorian England, when indoor plumbing was a wild new invention. A “closet” was a tiny room, and the “water” part was the flush toilet. So you’re literally walking into a room that uses water to vanish your business.
Why not just say “toilet”? Good question. In some cultures, “toilet” felt too direct or dirty. WC sounded polite and technical. Like a secret code for “please don’t ask what happens in here.”