There's also the obvious issue of that I highly doubt the author planned for someone as notable as the monster in the dark to be something that's not in the open license.
I mean sure, he uses Sunny now, but I don't know how secure he would have been way back when the monster in the dark was set.
Considering they aren't exactly wearing any clothes, either we would have known by now one way or another - or it's like Pokemon where apparently there are issues with them having a gender identity and gender attraction even though there's not way of actually telling what the other pokemon is.
Code words have many uses in battle actually. Not only are they shortening out, but even if it's easy to figure out, it could still take you a second or two to realize and your enemy will always have to consider what exactly do you mean.
A good example of that in the OOTS is in the desert, where V gave the instruction that Xykon is feeling chilly. Notice that it wasn't that obvious at first what it means to everyone (specifically Belkar).
I also loved this panel they had in Marvel back in Civil War 2. Someone was about to blast one of the heroes on their side, so Ms Marvel shouts : "Peter look out!"
Then Spiderman (Peter Parker), Colossus (Piotr Rasputin) and Star-Lord (Peter Quill) turn around and get distracted and all of them get blasted.
Then Ironman goes : "That's why we use code words in battle"