Why? It's a brackish water fish. Assuming we're talking about Gobioides spp. Various fish are sometimes sold as "dragon gobies", such as Rhinogobius duospilus. Good aquarists learn the Latin names and use them. That way, you'll always get information aout the right fish.
Nothing to apologise for. It's simply helpful to others (who may use different local names) and helpful to yourself (by ensuring you and your correspondent are both talking about the same fish). Similar common names are frequently used for completely different animals. There are at least two different chocolate cichlids and two different parrot cichlids, as well as numerous fish called "gar" and "freshwater barracuda" in the hobby. Common plecs can be anything in half a dozen genera, and "freshwater eel" is even less helpful. Once you have a Latin name though, everyone knows they are talking about the same thing.
My Violet Goby (Dragon Goby) has grown fairly slow.. I've had it a little over 2 years and it's around 11.5 - 12" long. I keep it's tank at 1.010 and it's in a 55 gallon.