The language is based on ancient Greek. This choice was likely due to the fact that many early Greek myths involved huge, winged beasts that spit fire and were dangerous to humans, which is similar to how Dragons are portrayed in European folklore.
Merlin has known how to speak in this language since The Last Dragonlord, where he inherited his father's powers and commanded the Great Dragon for the first time. His father, Balinor, also knew how to speak in this language, as did all Dragonlords.
It is unknown whether Kilgharrah and Aithusa actually communicate in this language, or if it's only a language that Dragonlords use to command Dragons. Kilgharrah, at least, seems to prefer to speak in English. He regularly used this language when communicating with Merlin, and also used it to speak with Gaius and Lancelot (A Remedy to Cure All Ills, The Darkest Hour).
Wyverns can also understand this language, and, like dragons, have to obey commands spoken in it by Dragonlords. However, the feral, animalistic nature of the wyverns makes them unable to speak it or any other known language (The Eye of the Phoenix, The Darkest Hour).
- Merlin commanding Kilgharrah to stop his attack (The Last Dragonlord):
- "Dragorn. Non didlkai. Kari miss, epsipass imalla krat. Katostar abore ceriss. Katicur. Me ta sentende divoless. Kar… krisass."
- Merlin summoning Kilgharrah (The Tears of Uther Pendragon, The Sorcerer's Shadow, The Darkest Hour, The Sword in the Stone, Arthur's Bane, The Disir, The Kindness of Strangers, The Diamond of the Day):
- "O drakon, e male so ftengometta tesd'hup'anankes!"
- Merlin taming the Wyverns (The Eye of the Phoenix) and Aithusa (Arthur's Bane, With All My Heart):
- "Nun de ge dei s'eikein kai emois epe'essin hepesthai!"
- Merlin ordering away the Wyverns (The Darkest Hour):
- "S'enthend' apokhorein nun epello-o-o."
- Merlin calling Kilgharrah to attack (The Sword in the Stone):
- "O drakon, fthengomai au se kalon su katerkheo deuro!"
- Merlin ordering Aithusa to leave him (Arthur's Bane):
- Merlin ordering Aithusa away from the battle (The Diamond of the Day):
- "Nun de ge dei s'eikein kai emois epe'essin hepesthai! Weas!"
- Dragon Language is based on ancient Greek.
- Dragons can communicate in both this language and in English, and are forced to obey any Dragonlord who commands them in it (The Last Dragonlord).
- According to Kilgharrah, "Aithusa" means "light of the sun" in this language (Aithusa).