[RPG] Does a PC who was KO’d earn experience for that combat

The ultimate and most ancient point system for "quantizing success through a numerical method" is, of course, money. Or perhaps predating even that, number of cattle, sheep, size of land controlled, etc. And war and trade were very early human activities to optimize that quantized success.

History aside, LordVreeg's answer above looks the most promising to me so far in terms of modern gaming.

Update

Since my original post, I have found a online-viewable citation that clearly credits David Arneson (co-creator of D&D with Gary Gygax) as creator of the "experience (point) system". It comes from a March 2008 Wired Magazine article, "Dungeon Master: The Life and Legacy of Gary Gygax" by David Kushner, and was written shortly after Gygax died (2008). It describes the creation/development/motivation of the experience point system this way:

Arneson tested his Chainmail mod in play sessions with his group and, based on their feedback, continued to tinker with the rules to make it more fun. ...

There was another aspect of the game he wanted to tweak: the fact that it ended. Arneson's group was having too much fun playing these specific roles to want to part with them after a single game. Outside of the individual games, Arneson created an experience system for characters. Your character would earn experience points based on their success from game to game. After a certain number of poins [sic], a character would "level up."

It does seem to be clear from this point that experience points were not in Chainmail and were Arneson's invention and part of his contribution to D&D. It does not necessarily rule in or out whether Areneson pulled the idea from somewhere else however.

Your question and other comments do leave me curious to know about ancient competitions (e.g. gladiators, tournaments such as jousting tournaments)-- whether they had any cumulative or longer-term rankings (based on win/loss ratios or #wins) that would be quantitative and cumulative in nature and thus similar to XP beyond what you'd just find in "sports".

I think it's a great topic worthy of intellectual and historical research. What you call "currency of achievement" is what I think of as a "Cumulative point system". As I've reflected upon my own behavior and others' over time, and beyond just the sphere of "games", I've found that cumulative point systems-- whether found in games, online forum reputation systems, or real-world systems like money -- tend to have three great virtues that make them addictive-behavior generating:

• immediate feedback (delayed feedback reduces addictiveness)
• clearly recognizable feedback (quantization adds clarity that increases addictiveness)
• effort compounds over time (benefits that last into the indefinite future are much more valuable than transient ones, increasing addictiveness)

Good luck with your research!

No, this isn't novel (although that does not mean that it isn't clever design in Numenera).

There are two separate things married in that mechanic as you've described it. Both have been done before, and I can think of at least one game that has married them in the same way before.

First there is the concept of a pull mechanic. Most GM-initiated events are examples of using push mechanics—the GM imposes something and the player has to deal with it. In a pull mechanic, something is offered at a price, and the player is faced with a tempting choice. Pull mechanics are not inherently better, but they do have some nice side-effects that a designer can take advantage of in ways that are different than push mechanics. Compels in Fate games work like this.

The second thing being joined here is a game currency that is the source of advancement. This is familiar to all of us as XP and isn't anything new. D&D does this, of course.

When you join a pull mechanic with advancement currency as the bait, you get a very neat mechanic that puts advancement and choice more into the players' hands. In my experience, that significantly increases players' sense of agency and control over their characters' destiny. (It's not fool-proof of course—the GM can offer bad deals—but you can break any mechanic if you try.)

The most well-known game that I can think of that does this is Apocalypse World (and its fantasy child, Dungeon World). The same bargains happen: here is a choice, and the choice is to accept trouble and then deal with it and get to mark experience, or refuse the experience and don't suffer the trouble. AW even calls it "experience". It's not as free-form as it sounds like in Numenera, but that's just a side-effect of the GM being bound by rules about when they can inflict "interesting" events on the PCs.

If you read designer blogs, after a while it becomes obvious that there are very few truly novel mechanics out there—they're all learning from and inspiring each other. What is novel is the way these small bits are combined into systems that create new rules-player interactions that we haven't seen before. Though they're pretty much identical, the XP pull mechanic in Numenera is almost certainly going to have different effects on the rest of the game system and the people playing it than the XP pull mechanic of AW does.