What is the origin of the terms used for 5e plate-based armors?

Question

This question came to mind when I was searching for historical examples of "half-plate" and found the term conspicuously missing from reliable sources. As far as I can tell, "half-plate" seems to be a term coined for use in fantasy and role-playing game settings.

Similarly, I'm somewhat confused about how a "breastplate" came to describe an entire category of armor when, so far as I know, breastplates are usually nothing more than components in larger suits of armor.

So, I'm curious to see if there's any information on the origin of the terminology used for plate-based armors in D&D 5e, such as:

• historical examples which may bear these names
• pop culture examples or previous editions of D&D which may have coined these armor classifications

For the purpose of this question "plate-based armors" means the breastplate, half-plate, and plate armor in D&D Fifth Edition.

I should also clarify that I'm not interested in discussion on leather armor and chain mail (on its own), as there's already a slew of information (and controversy) on the historical origins of these armors.

Answer 1

Breastplate and half-plate were added in late AD&D 2e to represent Renaissance-era lighter plate armor.

The summary is as follows:

• The term "breastplate" dates back to at least 1611 in the King James Bible, and was used by scholars in the 1800s to describe a piece of chest armor. It appears in AD&D as far back as 1980, and in 1995 described renaissance-era cuirass worn alone, becoming a main armor type in D&D 3.0 (2000).
• The term "full plate" dates back to at least 1909 in a book cited by Gygax himself, referring to the well-known type of full-body plate armor, and appeared in Unearthed Arcana (1985), although this type previously appeared in the original D&D boxed set as "plate armor".
• The term "half-plate" dates back to at least 1922, but did not enter D&D until 1995, where it represented a renaissance-era less bulky alternative to full plate.

Usage in D&D

Chainmail (1971) featured plate armor among its many armor types, but no breastplate or half-plate. Similarly, the original D&D boxed set's Men & Magic (1974) again featured plate armor as the strongest, but no breastplate or half-plate.

The AD&D 1e Player's Handbook (1978) introduced the term "plate mail" for its most superior armor. The Dungeon Master's Guide (1979) p.27, describes this as light chainmail with some plates, and also briefly mentions plate armor and field plate. On DMG p.165, Gygax cites Charles Ffoulkes' 1909 work Armor and Weapons as a source.

Half-plate and breastplate still do not appear in the AD&D 1e core rulebooks. As far as I can find, half-plate did not appear in any AD&D 1st edition sourcebook.

The term "breastplate" did appear in various sourcebooks, often describing a component of a more complete suit of armor. There are some instances of people wearing a breastplate alone, usually primitive tribes such as the Rovers of the Barrens (World of Greyhawk box set) or the people of Hyboria (Conan sourcebooks), and usually made of some inferior material. We do see a thief in Lankhmar sourcebook Swords of the Undercity wearing a breast plate alone.

Unearthed Arcana makes major changes to plate-type armor, and defines more clearly what each represents. Plate mail is chain or brigandine with some plates over vital areas. One point better is the new "field plate" armor, and one point better again is the "full plate" armor representing late middle ages and renaissance plates. AD&D 2e's Player's Handbook adopts these new armor types as standard.

AD&D 2e's Player's Option: Combat & Tactics (1995) introduces "half-plate" to represent a chronologically later form of plate armor, from a time when firearms became more prevalent, reducing the benefit of full-body armor. It covers the chest, outer arms, and upper legs. Historically, lower-leg armor was disadvantageous for soldiers who marched on foot, as it significantly increases the amount of energy used when marching.

Combat & Tactics also has a type of armor called "back-and-breast", which is a metal breastplate and backplate, based on armor worn during the renaissance. Historically, armor like this exists which was able to protect against a shot to the chest from early firearms, which was the most important risk to mitigate as firearms came to dominate the battlefield. Additional armor was an impractical expense and impediment to movement.

In D&D 3e's Player's Handbook, the armor list features breastplate, half-plate, and full plate. These are likely drawing on Combat & Tactics, which shares lead designer Skip Williams and was written only a few years earlier.

While D&D 4e's Player's Handbook ditched breastplate and half-plate, that edition was generally poorly received, and D&D 5e draws more from 3e. D&D 5e thus uses breastplate, half-plate and full plate. Of note, 5e recategorizes half-plate from heavy to medium armor; in 3e it was all-round inferior to full plate and never used, whereas now it's the highest-AC medium armor.

History of terminology

The word "breastplate" appears in the King James Bible, published in 1611. Revelation 9:9 says:

And they had breastplates, as it were breastplates of iron; and the sound of their wings was as the sound of chariots of many horses running to battle.

This book dated 1895 also uses it to refer to armor, suggesting (perhaps through Biblical use) it was still a word in common use at least among academics:

Sagard says that the Hurons (Iroquois) had armor made of wood. Champlain also describes the Iroquois' armor as amde of wood and thread. A plate in the same volume shows a warrior in armor. Wooden breastplates were worn. Copper breastplates have been foud, like the gold breastplates of Pero.

Breastplate explicitly referencing a metal piece of chest armor is similarly used in Andrew Lang's 1906 work Homer and His Age, an article which also quotes 1800s works on the armor worn by the Iroquois. It uses the word to describe Greek armor:

... by the seventh century B.C., a warrior could not be thought of without a breastplate; and that new poets thrust corslets and greaves into songs both new and old.

I can't find any similar historic reference to "half-plate" before 1899, so I'm skeptical that it was a term used at the time this armor was in use. However, it does pre-date D&D. Compton's Pictured Encyclopedia (1922) p.215, describes both "full plate armor" of the 16th century, and "half-plate" worn by 14th century mounted knights.

The term "full plate" appears in Charles Ffoulkes' 1909 work Armour and Weapons, which Gygax cites in the 1e DMG as a source.

Answer 2

Half-plate

Did the term "half-plate" exist before D&D? Well, probably not. It's difficult to say with any certainty that a certain term was never used anywhere in the wide world; but from what I can find, what D&D describes as half-plate -- armor that consists of fitted plates over the upper body with little lower-body protection beyond strap-on greaves and a plate or chain skirt -- is often called "half-armor", but the specific term "half-plate" seems unique to D&D and its descendants.

The most famous half-armor is probably Alemain rivet armor (a late-period mass-produced form of plate) or demilance.

I suspect the term "half-plate" was made up for the game in an effort to increase clarity, because "half-armor" is a bit vague and confusing in the game's context. However, short of a specific statement by Gary Gygax or Dave Arneson that claims credit for making up the term, it's unlikely to be provable.

Breastplate

Technically speaking, a breastplate is just the front-plate; a cuirass is the torso armor that consists of a breastplate and a backplate. That said, the terms appear to have been very nearly interchangeable for a few centuries, so getting overly technical on that point may not be in the interest of clear and concise writing.

I somewhat disagree that breastplates only exist as a piece of a larger suit, unless you mean a cuirass is a 'larger suit'. A cuirass is a very common piece of armor across the world, historically, and is still in use today in the form of the flak jacket or plate-carrier vest (or a bulletproof vest, to some extent). If you ask "did anyone ever wear a cuirass and nothing else in combat", then I could easily point to the United States military's modern tactical gear as an example.

But the same is true historically. In past centuries, most armies were not issued gear, but had to pay for their own armor and weapons, so personal wealth was the main determining factor of how much armor you wore. If you couldn't afford anything else, a nice sturdy anything over your chest and a solid helmet would vastly increase your chance of walking away from a weapon hit, and those pieces have a minimal impact on mobility since they're over areas of the body that largely do not bend.