WTSPT,
Do a search for ACP-131. If you can find the document online it gives a complete listing of both Q and Z operating signals.
I too have been told from a number of different sources that QNH and QFE stand for "question nautical height" and "question field elevation" respectively. The only problem I have with this theory is that as 4screwaircrew pointed out, these signals go back to the days of morse code and were used to provide brevity of transmission. Now if you were asking the question ie, What is the QNH then the morse code would be intQNH, that's how it would have been done in the military anyway. So that sort of contradicts the theory that the Q in the operating signal means "question". To follow that logic then every Q code operating signal means to question.
I think to come up with the DS solution you would have to find the crusty old military signals people who wrote these things up back in the days of valve operated, pedal powered radios.
Just as an aside, for anyone who has operated military radio eqpt. I have always been confused by the designator AN as in AN-GRC106. We were always taught that the AN stood for Army Navy (yet the airforce used the same kit). About 12 or so yrs ago I read a document out of the Army School of Signals that said the AN did not mean Army Navy but was a prefix given to all US manufactured communcations eqpt. Can anyone confirm or deny this one?