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!
Moldvay is great... in part because it's short. Tom and I spoke at some length about the 'tack' he would take. I later used a lot of ideas that he omitted because he just didn't have room. The following will address the BECMI treatment, being the most detailed expansion of Moldvay's data. At this distance (almost 30 years), most players consider the two nearly equivalent. (With apologizes to the ardent and more discriminating fans of either edition...)
Special Abilities are defined in BECMI, and summarized in the Rules Compendium (RC). The majority are Special Attacks, which include:
Acid, Blindness, Charge, Charm, Continuous damage, Disease, Energy drain, Paralysis, Petrification, Poison, Spell ability (1 per 2 spell levels), Swallow, Swoop, Trample
Some Special Defenses (Immunity to normal weapons, Spell immunity) are also Special Abilities.
Although the carrion crawler merits only one Asterisk by-the-book (for Paralysis), the overview of 'btb' is important: all of the published details are Guidelines, not rules. The ultimate choice always rests with the gaming group. Feel free to assign it an extra asterisk if you wish.
A counter-argument would be that the small (2' long) tentacles, while formidible, can rarely be directed at more than one target... and while that's going on, everyone else can hit it easily (AC7, unlike the AC3 head in AD&D) and its magic avoidance is mediocre at best (saves as Fighter L2).
But at the bottom line, the difference is 25 XP (per asterisk for a 3+1 HD monster), divided among the party... call it 4-5 XP per person. imho, not worth arguing about. So err in the characters' favor.
FM (author of BECMI)
Best Answer
It's worth noting that other early games did not use XP.
Timeline
1975 Tunnels and Trolls uses either AP (Adventure Points) or EP, depending upon edition.
Runequest (1976) and Traveller (1977) didn't use experience points at all.
1974 & 1976 † Original Edition D&D doesn't use XP nor EP. Electrum are mentioned, but non-standard, and Experience is spelled out.
1978 Starships and Spacemen, by FGU, abbreviates Experience Points to Exp. Pts.
1978 Holmes Basic D&D (Blue cover) spells out Experience, but does use EP for Electrum Pieces.
1978 AD&D Player's Handbook uses E.P. on page 20 (in the Cleric description) but nowhere else, and spells out experience everywhere else it's used.
1979 AD&D Dungeon Master's Guide uses X.P. and XP (many pages, defined on p. 230), and defines EP and E.P. as Electrum Piece (p. 228)
1981 Mechanoid Invasion (Palladium) uses Experience, spelled out.
As noted, 1981 Moldvay Basic D&D uses XP and EP.
Discussion
Therefore, Moldvay is not the origination of the use.
Moldvay also was not in print as long (it was replaced in 1983) where AD&D was in print with literally only cosmetic changes until 1988‡ or so.
Moldvay was quite popular, while it lasted, but had less lasting impact.
Therefore, it is most likely that AD&D is the popular source, not Moldvay's Basic D&D. Further, looking at many early videogames using XP, like Final Fantasy, the classes are closer to AD&D; the inclusion of Rangers, Assassins, or Druids, and separation of Race and Class are classic features of AD&D that were absent in Moldvay.
Footnotes
† 1976 revised some wordings and renamed several monsters due to a lawsuit from Tolkien Enterprises. ‡ AD&D 2 was announced, and AD&D 1 was no longer in print. 1E would be found in stores for several years on, as stocks in distribution continued to sell.