I was recently taking a sort of multiple choice quiz on just general Latin knowledge, and I came upon one question that threw me for a loop, so to speak. The question asked which of the options best described the differences between the question words -ne, nonne, and num. Using process of elimination, I found that there was only one answer where nonne was expecting an affirmative answer and num was expecting a negative answer. The problem was, however, that -ne was labelled as being used to express fear in the question. I have never really thought of using -ne in this way, and a quick lookup of the enclitic in Lewis and Short reveals just what I thought: that -ne was used for a question expecting a yes or no answer, or for emphasis. The word ne (negative of ut) can be used for fear clauses, but the question specifically had the enclitic form -ne. -ne is also used to add emphasis to a question, so one can see how this could be translated to fear in some way, but this seems rather a broad stroke to paint if one is trying to point out the distinctions between each of the words.
Therefore, my question is: can the enclitic -ne add specific connotations of fear to a question, and if so, are there examples of this in classical literature?