CHAINMAIL was a set of wargaming tabletop rules, that contributed to the creation of our hobby of RPGs, by initially providing a "Fantasy Supplement" that allowed including creatures like goblins, orcs, trolls, elementals, wizards and dragons; those rules were then adopted by Dave Arneson to create the first role playing experience, and led Gary Gygax to create D&D with Arneson's input. In the original version of D&D, the CHAINMAIL rules were still the default way to resolve combat.
In a recent question about some of the rules interactions, I did not think much to tag the question with chainmail, because usually we use game rules systems even for fringe games, and advise querants in our Q&A to always provide information about the game they are asking about (but that could of course also be done in the body of the question).
There are a few other questions that mention "chainmail" together with OD&D, or history of gaming but many of the questions with the word are about the armor type, so this tag could lead to confusion, if people tag questions about the type of armor with chainmail, and that tag is about the battle simulation system, not armor.
Should we use a tag for the system, and what should its name be?