What is the name of the ancient language used for magic in the 'Inheritance Cycle'?

The ancient language used for magic in the Inheritance Cycle is called the Ancient Language.

In Christopher Paolini’s world of Alagaësia, magic users shape spells by speaking words from the Ancient Language. The language is closely associated with elves, who speak it more naturally, but humans, dragons, Riders, and other trained practitioners can also use it. Its words do not merely function as arbitrary incantations: they express the intended action and connect magic to the nature of things.

A major rule is that speakers cannot deliberately lie while using the Ancient Language. This makes its vocabulary powerful but also dangerous, because imprecise wording can produce unintended results. Magic still requires energy, so knowing the language alone does not make every spell effortless.

The language is partly inspired by Old Norse, and terms such as “Brisingr,” meaning “fire,” reflect that influence. Urgals are a separate people with their own language, Dwarvish belongs to the dwarves, and Elvish is a misleading answer because elves commonly speak the Ancient Language but do not give it that name. The language’s true name is itself a significant mystery in the series.