Sort of a goofy question I know, but in writing done before RPGs popularized "melee" to refer to non-ranged weaponry I've only seen the word "melee" used to refer to a chaotic tussle or fight rather than a specific weapon designation. Is this a case of an RPG term being picked up by historians and medieval weapons enthusiasts, or was the word always used this way?
Google Ngrams suggests not. The only pre-1990s context in their corpus is still a "war gaming" manual, and even it does not use the term "melee weapon" (it only shows up because a table's formatting confused the OCR). Everything from the early 1990s is about RPG playing. This isn't definitive — not everything is in the Google Ngrams corpus — but it is pretty suggestive that the term was seriously not in use other than in this kind of context (one would expect at least one non-RPG hit if it was).
Changing it to the plural form gets you a couple non-RPG hits, but it is pretty few and far between (one of them is an OCR error).
Even just within gaming, the use of the word long predates RPG's. H.G. Wells' Little Wars (1913) miniatures rules appears to have been the first to use mêlée in the context of describing hand-to-hand combat in a game, and he notes in the introduction that it's something he invented (and named), specifically to deal with the lack of hand-to-hand fighting rules in earlier games. Later designs just followed Wells' precedent, and it eventually was transmitted to RPG's from the miniatures rules (Chainmail) that DnD developed from.