Originally posted by tasuki
Mmm... I think I'd have to ask a pro about that one, because I use it so much I just don't think about it anymore. Venturing a guess, I'd say it's a twist on the "na no da"/"na no desu" phrasing, which is redundant, but sometimes used for emphasis. It's mainly used informally in conversational situations, though, and the "da" is often cut out, in which case it sounds better to say na no, instead of nan. "nan" would be the contracted form of "na no". In the present tense "Sensei nan da", in the past tense "Sensei nan datta". (Of course, da is just short for desu, that at least, I'm sure of).
Thanks, Tasuki! I was wondering also about the "nante....na" construction, as in "Nante kirei na" or "Nante shinsetsuna (hito)nandeshou. In is redundant, isn't it??? And probably hopeless to reason out even this far....but for a semblance of order, it looks like "na" here is in its "na" adjective-role which is not to be confused with the masculine sentence-ending particle analogue to "ne"? And "nante kireinan" probably doesn't make sense either?