GMing

GMing is a relatively new word coming from the role playing game culture, which began to be used in the mid-1970s. "GMing" consists of the combination of the acronym of "GM" and the suffix "ing". "GM" is an acronym for "Game Master", which is the title given to the person that referees or "tells" the story in a role-playing game, such a RPG game of "Dungeons & Dragons". Thus, "GDMing" essentially means 'Game Mastering-ing', i.e. doing the task of a "Game Master".

Historically speaking, "GMing" started the tradition of gaming companies of "officially" providing a naming convention by giving a official sounding title to the referee of their role-playing game. It appears that TSR is the first game producing company to do so for their Dungeons & Dragons role playing game. GM was a sort of radical response of those persons, gamers or game designers that did not want to be exclusively associated with 'Dungeons & Dragons' or with 'TSR'.

Plus, "DMing" is also analogous to the task as a GM or Game Master, which in this case "GM" refers to someone that is the senior expert or the person acting as the Referee or Rules Interpretor of a complicated recreational game. Typically, GM is reserved for complicated tactics & strategy games, such as nearly any type of role-playing game or a tactics & strategy games such as the Starfleet Battles board game.

Since the mid-1980s RPG gamers frequently interchange the usage of DM with GM and DMing with GMing

The acronym GM is also closely gaming task associated of an ST, or Story Teller.