C'est Chiffonnette qui le dit
"Nay, from this hour shall none name me Túrin
if I live. Behold, I will name me a new name and it shall be Turambar!" Now this meaneth Conqueror of Fate, then the form of the name in the Gnome-speech is Turumart. Then uttering these words he
made a second time at the drake, thinking indeed to force the drake to slay him and to conquer his fate by death, but the dragon laughed, saying: " Thou fool! An I would, I had slain thee long
since and could do so here and now, and if I will not thou canst not do battle with me waking , for my eye can cast once more the binding spell upon thee that thou stand as stone. Nay, get thee
gone, O Turambar Conqueror of Fate! First thou must meet thy doom an thou wouldst o'ercome it."
J.R.R. Tolkien - HoME 2, The Book of Lost Tales, part 2 (T urambar and the Foalókë)