I've read advice before about the use of certain words when writing from specific perspectives. If writing from the viewpoint of an uneducated boy, don't let them know words that are beyond what reality would allow. However, there are some situations in which there is simply too much that the viewpoint character should not know, and I have no idea what alternatives to use to replace such words or phrases. In a piece I am working on, humans and the planet Earth do not exist in the known world. Since I am writing from limited third-person perspective, it makes no sense for my characters to use the words 'humanoid', 'humane', or even 'mankind.' Curses such as 'what the hell', 'what on Earth', and 'sweet jesus' (yes, really) are all out of the question as well. Has anyone else fallen into a situation like this before, and if they have, what sort of solutions did you use to replace those words and phrases?