During the Napolianic Wars there was a certain group of soldiers who had served with Napolean since the beginning of his empiric career. Due to the fact that they had served so long and close together, these soldiers felt free and comfortable enough to complain and grumble to Napolean about how things were being done. They didn't just grumble to grumble - but rather to encourage Napolean to reconsider and think about the tactics he was currently using. Napolean began to call the members of his "Old Guard" the grumblers or Grognards with affection.
Jump forward almost two centuries and you'll find yourself in the middle of the wargame craze. Wargamers, as rules and systems began to change, began to call those who stuck with "outdated" and old rules Grognards, specifically the ones who grumbled about how the old system was a better system than the current one. As RPG's enterd the gaming world, especially with its roots in Wargaming, the term eventually jumped into the RPG world.
Jump forward almost four decades and we have the end of 4th Editition Dungeons and Dragons and the announcement that 5th Edition is being designed. Just as those who stuck with previous editions and grumbled about newer editions, those who stick with 4e will be called Grognards.
4e is my Dungeons and Dragons, it's the one I cut my teeth on and the one I enjoy to play (I've played 2nd, 3rd, and Pathfinder very little), and I'm content to stay with 4e. (I plan on posting about 5e in the near future)
This is the home of the 4e Grognards, continuing to play and build upon 4e's fun!