Completely unimportant language misuses that bug you

[Peelee]

Of course both terms exist, else we would not be discussing this as no one would have ever heard of it. It is certainly prevalent, but that's not what I stated. If you go to a store (Lowe's,Home Depot, or whatever) and look at the tag or the box they will use the term water heater. That being said, the salesperson directing you there will certainly understand if you use "hot water heater." But, as the op wanted it is an "unimportant language misuse that bugs" my father. If the argument is that "it exists and is prevalent therefore it is not incorrect" then by the same logic nothing posted has been incorrect usage because all of them exist and are prevalent.

On that note, are you aware of linguistic prescriptivism vs descriptivism? The short, probably badly put version is prescriptivism adheres to a very definitive sense of correct and incorrect (which is effectively arbitrarily frozen in time and also contains rules that are not universally agreed on or do not logically follow, such as no splitting infinitives or ending sentences in prepositions), while descriptivism better embraces a living language and holds the idea that effective communication is paramount (I am obviously biased towards one here, I should note). So hot water heater is not incorrect at all from a descriptivist view.

Of course, lunaticfringe and I already joked about this in the beginning of this thread, and it's not a hill in going to die on to begin with (especially not in this thread; I don't want to rain on anyone's parade), but I thought you and/or your dad might be interested in it.