Well, according to MW online, revelation comes from "revelare" (to reveal), which isn't surprising. So, I wonder whether there's a Latin word "obvelare"? I doubt it, but it's worth asking. It seems the opposite of reveal would be conceal. So, since we have revelations, we should have concelations (or concellations), but we don't. Too bad. [I'm not discounting concealment here--just fooling around with reveal moving into revelation and conceal not moving into concelation -- or concellation.)