What is the origin of the word supernova?

Novas have been noted for over 150 years now. But until well into the 20th century, it was thought that all novas were pretty much the same thing, it's just that some were bigger than others. Today we know that a "regular" nova is a very different thing from a supernova, and one of the biggest differences is size. So the logical name for the better understood "large, hot star type of nova" was simply to call it a "supernova". It is not the same thing at all as a "regular" nova, it's mechanics and chemistry are very different.