Warning: SPOILERS for House of the DragonDaemon (Matt Smith) and Rhaenyra Targaryen (Milly Alcock) speak in High Valyrian to each other in House of the Dragon, which is laced with different coded meanings. Set 200 years before the events of Game of Thrones, House of the Dragon brings to life Westeros at the height of the Targaryen dynasty's rule over the Seven Kingdoms. In House of the Dragon episode 1, "The Heirs of the Dragon," teenage Rhaenyra is named heir to the Iron Throne by her father, King Viserys (Paddy Considine), which displaces her uncle, Daemon, as the next in line to be King.
The Targaryens hail from the Valyrian Freehold in the continent of Essos, and the family escaped before the Doom of Valyria destroyed the city by volcanic eruptions 200 years before House of the Dragon's timeframe. The Targaryens settled on the island of Dragonstone before Aegon Targaryen and his sister-wives, Visenya and Rhaenys, conquered the Seven Kingdoms, which ignited the Targaryen family's rule over Westeros for the next 300 years. Although the "common tongue" is the language spoken in Westeros, which the Targaryens are fluent in, House of the Dragon establishes that the dragon riders also speak to each other in High Valyrian. This is notable because by Game of Thrones' era, the Targaryens have been wiped out, with only Viserys (Harry Lloyd) and Daenerys Targaryen (Emilia Clarke) as the clan's survivors at the start of the series. During her exile in Essos and rise as Queen, Daenerys spoke High Valyrian to her translator, Missandei (Nathalie Emmanuel), indicating that the Targaryens did teach their children their mother tongue up to Dany's generation.
House of the Dragon makes it clear that along with using the common tongue, the Targaryens speak to each other in High Valyrian, usually in private. In "The Heirs of the Dragon," Rhaenyra and Daemon have a conversation in the Red Keep's throne room that begins in High Valyrian before shifting to the common tongue. (Although, it's also possible that their entire exchange was in High Valyrian and only shifted to English for the sake of the audience.) Rhaenyra and Daemon speak in High Valyrian again during the funeral for Rhaenyra's mother, Aemma (Sian Brooke) and her infant brother. The princess then ordered her dragon, Syrax, to use her flame to light the funeral pyre with the familiar High Valyrian command every Game of Thrones viewer knows: "Dracarys!"
What Daemon & Rhaenyra Speaking In High Valyrian Means
Rhaenyra's High Valyrian throne room convo with Daemon is especially loaded for a few reasons. Both were aware that they were not alone; Ser Harold Westerling (Graham McTavish), the Lord Commander of the Kingsguard, was listening in to protect the princess. So Daemon and Rhaenyra used High Valyrian to keep their words private between them since Westerling only knows the common tongue. Further, Rhaenyra was teasing Daemon about his mistaken belief that he was the heir to the Iron Throne, and she knew that King Viserys intended otherwise. Most importantly, uncle and niece knowingly used High Valyrian seductively as a language of romance, and it set up the flirtation between Daemon and Rhaenyra that will escalate into the physical (as is the way of the Targaryens) in later episodes of House of the Dragon. At the funeral, speaking in High Valryian kept Rhaenyra's hurt over her family and her fears about her father private for Daemon and away from the ears of the Westerosi in attendance like Lady Alicent Hightower (Emily Carey).
After the Doom of Valyria, High Valyrian stopped being a living language on Essos and mutated into a different form called Low Valyrian. In general, no one in Westeros but certain scholars can read, speak, or understand High Valyrian. But the Targaryen ruling dynasty has obviously maintained High Valyrian as a language spoken by and within the family, which they use to their advantage to keep certain conversations and matters private from their subjects. Every time High Valyrian is spoken by a Targaryen in House of the Dragon is likely to be important and laced with extra meaning and significance.
House of the Dragon airs Sundays @ 9pm on HBO and streams on HBO Max.