The Q codes were developed when communications wasn't as
good as now, and Morse code was till the norm.
It was a lot easier to shorten things down, made life a lot easier
on the wireless operators if they only had to send a few letters
rather than a whole sentence, and also was less likely to be
misinterpreted. Anyway, the Q stood/stands for question, and
NH stands for Nil height. In Europe an ATIS will always include
QNH and QFE. If you set the QNH, you can report your SL as "altitude
QNH", whereas if you report QFE it will be understood you
are reporting height above field elevation. Understand that QFE
derived from Q code Field Elevation hence QFE