[@ShyDot]

Kilgarrah and the primevals are all named after dragons from various mythology or other works of fiction.  Kilgarrah is from arthorian legend, described as the 'greatest of all dragons', and aiding merlin at one point before being sealed under camelot. Fafnir, Niddhoggr, and Jormungand are from Norse Mythology, fafnir being a dwarf that turned into a dragon, Niddhogr a dragon born from loki that was trapped under the world tree, and Jormungand, Niddhogr's brother that was described as a massive serpent as long as the world itself. 
Mizuchi and Ryujin are from eastern mythology, Mizuchi being a water dragon spirit, and Ryujin the Dragon God. Typhon was the greek God/titan of monsters, described as a multi-headed man-dragon/serpent. Smaug and Ancalagon were from tolkien's writings of middle earth, Smaug being famous from both the books and movies, and Ancalagon being the largest dragon ever, and led a siege of dragons on sauron's will eons before lotr timeline. Tiamut and Bahamut are from Dnd (Although Bahamut is also from FF), as the two main Dragon Gods, Tiamut being a five headed evil dragon, each head representing an element, and Bahamut a platinum dragon of justice and honor.