In the Fleming novels M stands for the character's last name, and I think his whole name is Sir Miles Messervy. The movies have carried on this tradition with other characters (Mawdsley, Mansfield, and Mallory) rather than explain why Bond's superior is called something else other than 'M'.

'Q' stands for Quartermaster, who is the person 007 sees to obtain the gadgets he will be using for the mission. 'M' is the codeword given to the head of MI-6. In the Fleming novels, 'M's name was finally revealed in 'The Man With The Golden Gun' as Sir Miles Messervy.

M is a codename held by a fictional character in Ian Fleming's James Bond book and film series; the character is the Chief of the Secret Intelligence Service for the agency known as MI6. Fleming based the character on a number of people he knew who commanded sections of British intelligence.