The name of this blade is Elder Speech and translates as mountain fire or greatest fire. It was quite likely inspired by the real world family of flame-bladed swords: flambards, flammards and flamberges.
The Witcher[]
Ard'aenye is a sword which used to be found during Chapter IV of The Witcher, the first time Geralt entered the fields. It is no longer available in the game, but does appear to be the same model as the sword used by the Grand Master of the Order of the Flaming Rose. It closely resembles the description of a gnomish gwyhyr in the novels.
In the Enhanced Edition, Ard'aenye was once obtainable and used to be found during Chapter V of The Witcher, inside Raven's crypt, in the swamp cemetery. It was found inside one of the graves of graf Corbus de Ruyter with the Remains of Raven's Armor. After the last patch update, Ard'aenye was replaced by a meteorite sword, regardless of the description in the Enhanced Edition's official Game Guide book on page 105.
There are actually two steel weapons called Ard'aenye that Geralt can use on the first game, one is the copy of the sword used by the Grand Master, and the other is the heavy mace used by the class of mutant known as Greater brother, however the Ard'aenye heavy mace can only be equipped using a Save Editing Tool and unfortunately is not possible to tranfer the weapon to the second game using the save import system.
The Witcher 2: Assassins of Kings[]
Ard'aenye can be imported from a saved The Witcher game into The Witcher 2.
The Witcher 3: Wild Hunt[]
Ard'aenye is a steel sword in The Witcher 3: Wild Hunt.
It can only be found as random loot, known to sometimes spawn in a guarded treasure south of Devil's Pit in Velen.