I've probably talked about this before, but I wanted to address it again. I'm not sure where the folk-terms for armor and weapons that pervade dungeons and dragons (and some fantasy stories from the early 20th century) arose from. But they are flat out wrong, and make a general muddle of a topic that could be much simpler.
Further, the great swathes of armor listed in the AD&D 2e PHB were never historically used alongside one another, making it strange to imagine acquiring a chain byrnie alongside a fellow wearing a full suit of plate armor.
Anyway, here are two of my least favorite misnomers:
There is no such thing as a greatsword. The word longsword probably emerged from the 17th century German lang schwert which referred to two-handed blades like Renaissance Zweihanders. The thing that fantasy and Dungeons and Dragons insists on calling a longsword is an arming blade. This is the one-handed, generally cruciform, sword used by your average knight.
Mail means chain armor. There are a lot of alternative ways to refer to chain armor: a hauberk (short shirt of mail), haubergon (long tunic of mail), byrnie (long tunic of mail), etc. There are mail chausses (the leggings), mail gloves, and the aventail (mail hood). But there is no such thing as plate mail. There is, however, plate armor. Plate armor was universally worn with mail beneath or interstitially, leading to the term plate-and-mail, which is perhaps where the confusing origin of all these different types of "mail" spring from.
But if you're talking about mail, you're talking about chain links. Saying chain mail is redundant. It is either chain armor or simply mail.