The person who runs a roleplaying game is often called many things: Judge, Referee, Aedile, Storyteller, etc.
However, D&D popularized the term Dungeon Master, usually shortened to “DM”. A closely-related term is Game Master or “GM”.
I talk about D&D a lot, so why don’t I use the term “DM” in reference to myself?
For some reason, my brain associates “Dungeon Master” with sexual fetishes that I want nothing to do with.
Thus, I prefer to use Game Master / GM for myself. I do not mind using DM when referring to others, particularly if it is their preferred term.
TL;DR I’m weird.