We say that those are "grown-up words" and not appropriate for children to use. We haven't had any problem with my 4 yr. old swearing, although he did get away with "what the hell" for a while before we decided that one is swearing. 
We easily exchanged it for "what the heck" or "what in the world" and occasionally, "what the heck in the world?!" A reminder of, "that's a grown-up word" and we generally won't hear it from him again.
We easily exchanged it for "what the heck" or "what in the world" and occasionally, "what the heck in the world?!" A reminder of, "that's a grown-up word" and we generally won't hear it from him again.
