"dracarys" was coined by daenerys, as she didn't want her dragons to burn everything and everyone by using a simple command that could be said by just anyone, so she added the words together and formed, "dracarys", because not everyone was fluent in high valyrian.
i'm curious about how this is supposed to work. maybe the targaryens before her did actually use this word and it wasn't known to dany? what are your opinions?