Getting Into "Hot Water"

What is a "hot water heater", and why is one needed? Why do we need to heat water that is already hot? Why not just call it a "water heater", which is what it really is?

Another peeve of mine is the word "vehicle". Folks, it is pronounced "v-ick-el", not "v-hick-el". The "h' is silent. But what gets me is the fact that so many people have been using the v-HICK-el pronunciation so much, that it has become an accepted form of the word. But that doesn't make it correct. I learned the correct pronunciation in the eighth grade.
Everyone from presidents, doctors, engineers, and yes, a few scholars, pronounce it incorrectly. It's no wonder that Americans are falling behind the rest of the "civilized" world in education. We can't speak our own language.
If you say ve-HICK-el, then you are most likely a hick. And the heck of it is that I'm from Tennessee, the birthplace of hickdom.