If they understand that language well enough to know the chap’s name was OBSIDIAN, why wouldn’t it mean what it has always meant: A type of rock that all those ancient cultures used and shaped into various tools and weapons. Obsidian knives have been legendary, surpassing our modern scalpels for surgery. It has even been claimed that an incision made with an obsidian knife will heal faster than one made with a metal knife. FWIW.
It appears that it’s a term with more than one use; analogously, a man can be called a rake.
Mayans were part of the Obsidian Order?
Man, the things you learn.