It's weird that a room with just a toilet and sink is called a "half bath", when it in fact has zero bathtubs.

Clearly you've never half-bathed in gas station restrooms while hitchhiking cross country. Hint: it doesn't involve the toilet.
But I'm puzzled that a room with only one plumbing fixture is called a "quarter bath" regardless of whether that fixture is a sink, toilet or shower. Dat don't make no sense.

So is this a good time to bring up Hillary's email server? Cuz I thought merely using an improperly secured server was a super huge deal to conservatives, many of whom screamed treason and demanded prison for her. And I don't think any vital information was ever actually leaked through it.

True, we should call it the "shit 'n rinse."
- Excuse, where's the shitrinse located at?
  Would you mind if I used your shitrinse?
  Yeah I think it works.

It is half a bathroom
No you don't get to ask why a bathroom is called a bathroom. It is like questioning the origin of a hot dog.
- It's a euphemism. "Water closet" is another old fashioned word for a bathroom.

On the other hand, if you say you are going to the bathroom, nobody expects you to take a shit in the bathtub
- Which is what makes it all that much more satisfying when the next person goes in

Never heard "half bath", and I always called those washrooms.
- Real estate term.
- It is common in the US, frequently they will be listed as 2 & 1/2 baths if they have two with tubs and one without.
  Haven't paid enough attention to know how they list multiple 1/2 baths but pretty sure they don't add up like regular fractions...
  I always found the term 1/2 bath weird.
  
  that's some realtor math. they are known to magically inflate surface before you buy it, and shrink it back once you bought / rented it. Mathematicians can't explain that !
  
  And a room with a toilet, sink, and shower stall is a 3/4 bath.
  
  Haven't paid enough attention to know how they list multiple 1/2 baths but pretty sure they don't add up like regular fractions...
  They'd either list them separately or as a whole and then clarify. E.g. "two full- and two half-baths"or something like "four bathrooms - two full"
  
  Imagine getting a half bath but only the back half so you don't even get a faucet
- Whatever we call them, it's always some euphemism hiding the fact tha it's the pooping room.
  
  We call it the poop stick room.
- Commonly called called a 'powder room' in australia.
  
  Maybe it's a class difference thing but I've more commonly heard it referred to as "the shitter," "dunny," or "toilet."
  
  Powder room is where you store amino.
  
  or "water closet" in the UK
  
  I’m in the US and powered room is used in places I’ve lived. But on real estate listings it is common to call it 1/2 bath.
- It's a way to conveniently talk about the number of bathrooms. You can say a house is "three bedroom, two and a half bath" and you convey that there are two bathrooms and one "washroom".
  
  Or 5 powder rooms and zero bathtubs
  
  What gets confusing are these large homes, or McMansions that list 5 bedrooms and 7 and a half baths. So are they listing 3 powder rooms at 1.5 baths? I can’t afford them, so I only see it online; but that part gets weird. I have seen descriptions that then list full and partial though.

You can bathe half your body in the sink and the other half in the toilet.
- Bidet ftw.
- And now I'm going to touch grass
  
  Don't forget to bathe after!
- Cursed comment, but I’ll add on to it: If you plug the door slit with a towel the whole room becomes your tub.

Bath doesn't refer to the tub, it refers to bathing. You can 'sink bathe' with a rag and running sink water.
So a half-bath, contains 1/2 of the common furnishings for bathing.
- Yeah, a "full" bathroom with just a shower also has zero bathtubs.

The real weirdness originates from any room with a toilet being called a bathroom despite many not having bathtubs.
- Technically if it doesn't have a bathtub or shower it is called a powder room. But that phrase is rarely used. (Mostly because 90% of the time when we say bathroom we mean toilet.)

You'd be amazed how much bathing some people manage to do with just a sink.
- Probably around half?
- You've been to McDonald's I take it

At that point you're halfway to having a standard bathroom, so it makes sense to me.

We'd just call that room "the toilet"

And in the UK a “cloakroom” is very rarely a place specifically to hang your cloak…

in german that room is just called "das klo" (the toilet)
- *Klo
  
  thx, fixed the typo, dam phone keyboards being so small

Good news! Most of the world would find that extremely weird (as with calling a room with no baths a bathroom). I think it's due to the euphemism treadmill.

If you chop a bathtub in half and place the parts in different rooms, you can have two half baths. If you bring four such parts in the same room, you’ll get a double bath. Probably still not very good for actually bathing, because a half tubs don’t hold much water.

And if you had half a bathtub, you could as well have no bathtub at all
- If it's fixed to a waterproof wall, it would work. Weird, but work.

We call it a trap, khazi, bog, privy, WC, toilet…don’t think I’ve heard “half bath”.

You're right. It should be called a 2/3 bath instead.

sailing by in my half-boat "YEAH that is just like.. your OPINION MAN!!"
oh fuck wat.... ....🐟 ....🪸 🦴 🚢 🌊 🤽
- You would have been fine if it was a Boston Whaler.
  https://youtu.be/W7V-2_tyRAk

By code a bathroom is a sink and any combination of a bidet, shower, tub, or toilet.

Showerthought: You could technically have a three-bath house with zero showers or bathtubs, just six little sinks all over.