Languages Smaug spoke?

[Inziladun]

Originally Posted by Barrel-rider

But weren't at least some dragons bred by Morgoth and Sauron? Because Dark Tongue could apply here if that's so.

Dragons originated from Morgoth. It was Sauron who devised the Black Speech, and I know of no indication of Sauron 'producing' any dragons.

It was said the Black Speech wasn't very widespread anyway, by the time of the Third Age only remembered by the Nazgûl.