We electricians have developed a language simply to make things more complicated then they actually are, well that’s my theory anyway. So many things can’t be explained with logic.
Three way switch has three terminals. 4 way has 4 terminals. Yet we don’t call a 2 terminal switch a 2 way that’s a single pole. A 2 pole also has 4 screws too buts that’s different so not a 4 way…
Everyone I deal with calls the carriers but travelers wouldn’t get a blank stare I’ve heard them referred to as travelers as well. If you asked for marrettes you’d get a blank stare
I figured that. 
The easiest way to keep the ways straight is to realise that with a three-way switch there are three terminals that will at some point or another have current flowing through them. A four-way switch has four terminals providing a current path at one point or another. A Double-pole single-throw could be said to have four “ways” but as boytyperanma says you would never call it that in the field because it’s not what people want when they ask for a 4-way switch.
I work in automation and we have a lot of hydraulic and pneumatic control valves (solenoids) where the same terminology is used in determining what valve you want for an application. They get even more confusing again because there are so many different combinations out there.
Appliances don’t bother me so much, I think because they aren’t “built-in”–at least where I live. Look in the lightswitch aisle of Home Depot, and you’ll see it is a growing trend to emblazon the company name on the front of the switch or the switchplate.
But then again, I took off all the name plates from my luggage, as well as coats at times.
Still, it is nice to know from this thread that I am not the only one irked by this.
I’ve swapped out 3-way switch installations so that both up or both down = off & one each way = on. The opposite parity bugs me.
As with others above, I also dislike the growing trend to stick ever more prominent brand names on ever more merchandise. Brand names on light switches? … F**k that company; I wouldn’t buy 'em.
Having a 4 way switch might make your head explode. Be careful in future home purchases.
Three-way switches are used to control lighting from two different locations. If you want to control it from three locations (or more), you must install a 4-way switch (or more) in the circuit. See other posts for the difference between the devices.
I lived in a place that had one of those… by the front door. Well, OK, it was an apartment, so it was the only door. I must have spent over an hour trying every outlet in the place, plus looking on the ceiling and wall outside for some sign of a light fixture that has been removed at some point. No sign of anything. I even took the faceplate off and looked in the box. No wires at all near the thing. What bothered me more for a while after I moved was that I had forgotten to ask the office what it might have been for.