Dragoon, and its family, have an unique type combination, however, in ORAS, another Pokémon with the same typing came to be, in Mega Sceptile.
It shares the same name as Dratini's Beta Name.
Droot is based on a Dragon Froot mixed with European Dragons, the way it is designed makes it seem more like that of a Pupal Stage seen in an insect which this trait is seen with a few reptilian canonical Pokémon in their Middle Stage, those being Shelgon and Pupitar.
Dragoon's name is a combination of "Dragon" and "Cocoon" and Possibly even "Goon".
In other languages
from Pitaya (Dragonfruit), Drache (Dragon) and Kapsel (Shell)