First of all, when you're in public, everybody calls them "restrooms", but when you really think about it, that name is rather misleading, because it implies that the purpose of the room is for you to waltz right it, climb in bed, or pull up a chair, have a beer, watching TV, lye on a couch, take a nap, that sort of thing. When you go into a restroom, there's no resting involved!
Secondly, informally, everyone refers to it as the bathroom, now although that's more correct, it too is misleading a bit, because it implies that the purpose of it is for you to walk in and take a bath, and that's pretty much, when in fact, more people step into the bathroom to anything but 90% of the time.
So if you ask me, they shouldn't even be called "restrooms" or "bathrooms" at all, I'm thinking something more along the lines of "Striproom" because think about it, everytime you walk into a bathroom, you always drop your drawers, or take you clothes off for a shower. Or maybe something like "Funroom" because the possibilities are endless since a lot of people find taking baths or showers fun, and little kids ALWAYS flush stuff down the toilets, or let the sinks over flow. Or maybe even "Water-room" since everything in there has something to do with water - the sinks, the toilets, the tubs, the showers...
You know what I mean?