"Dumbledore'd bewitched this branch to burn fer evermore, which isn' somethin' any wizard could do, an' so I lies it down in the snow by Karkus's feet and says, 'A gift to the Gurg of the giants from Albus Dumbledore, who sends his respectful greetings.'"
-- Hagrid (OP20)
Gubraithian Fire is a form of magically-created fire that burns forever. It is also known as Everlasting Fire. Flitwick mentioned it in Charms (OP20).
Dumbledore sent the Gurg of the Giants a branch enchanted with Gubraithian Fire as a gift to open friendly relations (OP20).
Scottish Gaelic "gu bràth" - forever