Q Codes from the British Admiralty, the 1912 International Radiotelegraph Convention et seq originally designed for morse to shorten transmission of repeated and predictable phrases. The letter Q being used at the start of a three letter code because it is relatively distinctive and not much otherwise used, the two subsequent letters (sometimes) having some attached meaning. For instance 'FE' allegedly relates to 'Field Elevation', 'NH' to 'Newlyn Harbour', 'DM' "Direction magnetic' (or 'magnetique') although I can't find any evidence for this and they may just be later mnemonics.