Your argument is essentially "just because the correct word IS in the dictionary and the wrong word ISN'T doesn't mean I can't use the wrong word anyway," which makes about as much sense as saying "just because the word 'carburetor' IS in the dictionary doesn't mean I CAN'T call it a 'gas disperserator' instead."
It's called a damper. Dampener is a term that tennis players made up out of ignorance.
Nope--I do not admit it is the wrong word (and to refute the assumption in your argument, "dampener" (unlike "dipserserator"--see below) is in the dictionary as an alternative noun form of "dampen" (think of it like a gerund, but in reverse--i.e., the verb forms of nouns are often listed as alternative forms of the word in question yet not given separate listings)), simply not the most common usage (at least in non-tennis situations) and thus it is not "made up". You either misunderstand or misstate my contention and again use the strawman/
ad hominem argument with no basis for the assertion and to irrelevant effect. I would also note that I could not find a listing or an alternative form indicating the existence of the word "disperserator" in the dictionary I have handy (MW's Collegiate)--but I will take your "word" for it (and might even give you credit for it in Scrabble
). Perhaps that was your point -- you can use a word not in the dictionary--if so, it is non-responsive, as "dampener" is indeed in the dictionary as a noun form of dampen and as used, conveys the same meaning as "damper"--so it should not otherwise be disqualified from use.
Irrespective of its origins, manufacturers, marketers have managed to make "dampener" a real enough term to name their product, mercilessly taking advantage of ignorant tennis players; charging fifty cents more for a dampener than they could have for a damper (poor saps!). Now, seriously, this is the last I have to say on this amusing but quite insignificant detour from this thread.
Thus, I will return us back to our regular programming and agree that all the little vibration "thingies" do is change the sound of the impact of the ball to the strings, much to my personal joy. We do agree on that point.