D&D General What “hit points” is?

[Tony Vargas]

"Each hit scored upon the character does only a small amount of physical harm..." - Gygax, DMG, page 82

Yeah, that's part of one sentence out of a long treatise that's trying to explain that hit points aren't just physical damage, so, no, contrary to contemporaneous mockery, your character does not swell to giant proportions as a consequence of gaining hps.
On the preceding page, under Poison Saves, he also explains that, when a PC makes a successful poison save vs an insinuative poison, there's no wound, not even a scratch.

I theory, in 1e, if you were, say, fighting a Purple Worm, and it hit you every round with the stinger, but not the bite, and you made your save every single round, but it finally dropped you to zero hps, you'd be dying without a mark on you.

So far as I know neither 2e or 3e redefined the hit point.

No subsequent edition has re-defined hps, in fact, 1e and 2e /barely/ even tried to define them, resting on the 1e DMGs laurels, as it were. 2e has one extremely vague, quite straightforward sentence on the topic, for instance - as befits a settled issue, I suppose.

The general idea that a higher level character was, for a given amount of damage, turning that damage into a less serious of would through skill I'm pretty sure remained consistent

Once again, you're stating only part of the ideas put forth in the 1e DMG, an incomplete summary that loses quiet a bit. Not just less serious but no wound at all was a very real possibility. And it could have been skill, or luck, or divine favor, or a preternatural "sixth sense" - or combinations thereof - or quite possibly other things, the door was not exactly slammed shut.
It was a long, treatise, again, and it threw out all kinds of ideas.

4e abandoned the older description and 5e has largely followed the 4e model.

Abandoned is very much the wrong word, the idea that hps were mostly non-physical, but also a little bit physical, at times, was retained - it was just made more consistent on the mechanics side. 4e added a definite point at which (minor) wounds start occurring: the Bloodied condition at half-hps. 5e removed the condition, but put the same concept in a sidebar about DM narration of hp loss - so, at the DM's option, you could go back to taking no wounds at all until you were dying, or get scratched up a bit from the first wound that did a non-trivial % of your max hps, just at the whim of the DM rather than the dice.
4e & 5e get away with a more consistent conceptual treatment of hps because they've largely eliminated poison save-or-die attacks, so there's not the strong need for the poison save to represent a 'pseudo-hit,' as we used to say back in the day.

More significantly, in terms of the driving force behind the edition warring that resurrected the hp controversy, this time with Defenders of the One True Way of D&D on the opposite side of the argument (back to insisting that hit points must be all-physical, exactly like those mocking the concept of gaining HD with level back in the 70s), 4e stayed with the concept of hit points when introducing new mechanics like self-healing 'surges' as a PC resource and inspiration as healing for the warlord, removing the niche protection that magical healing had formerly 'enjoyed' (and removing the 'healing burden' from the cleric, eliminating the band-aid/heal-bot stereotype) and also making longer adventuring days more plausible.

TL;DR: Ultimately, the way hps work - as a highly abstract mechanic rating the creature's abiltiy to stand up to the deadly threats of combat & adventuring, that cannot be adequately conceptualized as merely physical durability, alone - has stayed constant through all editions.

 

[Maxperson]

Yeah, that's part of one sentence out of a long treatise that's trying to explain that hit points aren't just physical damage, so, no, contrary to contemporaneous mockery, your character does not swell to giant proportions as a consequence of gaining hps.
On the preceding page, under Poison Saves, he also explains that, when a PC makes a successful poison save vs an insinuative poison, there's no wound, not even a scratch.

I theory, in 1e, if you were, say, fighting a Purple Worm, and it hit you every round with the stinger, but not the bite, and you made your save every single round, but it finally dropped you to zero hps, you'd be dying without a mark on you.

Not really. What would happen is that at some point the portion on poison would come into direct conflict with the portion that says that there are a certain number of hit points that are purely physical. Per the hit point section of the 1e DMG, it isn't possible to hit 0 without taking purely physical damage in 1e.

That's in the actual hit point section, which would give it priority over the poison portion, since the poison portion is just trying to explain away why the PC doesn't die. Well, you can do that by simply narrating the tail hitting the PC, but the stinger itself not breaking the skin. That satisfies both sections.

 

[Tony Vargas]

.What would happen is that at some point the portion on poison would come into direct conflict with the portion that says that there are a certain number of hit points that are purely physical.

That wouldn't be an unreasonable call, and it would kick in somewhere south of the hypothetical max of 23 hps for the toughest possible 18-Con high-level fighter, who might well have 100+ hps.
Of course, he could also fail that first save and drop dead of a fatally-envenomed scratch.

Hey, it was still the 70s.