I was watching Tensei Shitara Slime Datta Ken (2013) and a character in there is said to be a Dragonoid, the offspring of a human and a dragon. Then I remembered Dragon Quest (2020) also features a character which has a Dragonoid form, a race created by gods with the features of humans, dragons and darklings (not sure if they are in the original 1991 version).
Then I looked for more info in internet and I found that Dragonoids are also a race in an anime called Bakugan (2008).
Doing further research, I found human-dragon hybrids have also other names, such as "draconic humanoids," and they are also featured in comics, novels and videogames. A Tale of a Human Dragon Hybrid trilogy books (unsure date) of course features one.
Mortal Kombat: Armageddon (2006) features hybrid dragons which are a cross between dragons and humans.
Wrong Time for Dragons (1997) also features an offspring of a human and a dragon
In Firebreather comic (2003) , a woman and a dragon have a half human-dragon baby.
Note I'm not referring to the trope of dragons being able to turn into human form when that's a trait of their dragon race; that would be a pure dragon not a hybrid.
Where does this idea come from? Which was the first fantasy story to feature human-dragon hybrids?