This is inaccurate, yes Dragonborn come from late 3.x, but they aren't renamed Half-dragons. They come from a semi-obscure supplement called Races of the Dragon. There they are called "Dragonborn of Bahamut", but instead of a true breeding race, they are part of the trans-human races that were popular with designers by then. (They were humans who made a ritual to Bahamut and became draconic as a result)
It cashed out as
effectively a level+0 template which could be applied to any non-evil creature with at least Int 3. Which means that a lot of things we think of as "animals" (technically, in 3.X terms, "magical beasts") actually qualify for such a transformation!
But yes, the "Dragonborn of Bahamut" (and their cousins, the "Dragonspawn of Tiamat") were transformed people, rather than a species in their own right, with the art showing examples from (implicitly) human, dwarven, gnomish, elven, orcish (or maybe goliath?), and possibly other origin species. Though they tried to go for a very uniform head-shape in
most of the art, the first proper image (not counting the section-opening sketch thing) looks much more similar to how 4e dragonborn ended up.
Heck, if you go with dragon men created from ritual, then you’ve got to include draconians from the early 80s. Between them and saurials from Azure Bonds, I think the inspiration for playing a dragon humanoid has been there for a long time.
We can go back much further, even. The
Spartoi--literally "sown ones"--were powerful warriors arising from ritually sowing dragon's teeth, which shows up in two different myths, one about Kadmos, the other about Jason's quest for the Golden Fleece. With the former, the teeth came from the Ismenian dragon, which was apparently one of Ares' sons; five of the Spartoi survived and went on to found Thebes, while Kadmus and his wife were vengefully transformed into serpents themselves by Ares. "Drakaina," literally just the female form of the Greek word
drakon, were known to be powerful sorceresses, some of whom mated with heroes to found dynasties in foreign lands. E.g. some Greek legends attribute the Scythians as descending from a
drakaina who persuaded (or coerced) Herakles to mate with her; scholars suspect this is a Hellenized version of a story imported from Scythia. In renaissance art Erichthonios, the "son" of Athena, was sometimes depicted as having scales on at least part of his body; he was strongly associated with serpents and was said to have a snake's tail. ("Son" because complicated narrative gymnastics ensue to let Athena have a son while remaining a virgin goddess.) Then there's the
drakon ophiogeneikos, literally "dragon of the serpent-born," who produced the aforementioned "serpent-born" by union with the nymph Halia when she came to the sacred grove he guarded.
So, yeah--whether transhuman, cursed, ritual-created, or (un)naturally-born, there's actually
plenty of precedent from Greek myth alone for dragon-people.