В приложениях к Властелину Колец о троллях сказано следующее:
"Troll has been used to translate the Sindarin Torog. In their beginning far back in the twilight of the Elder Days, these were creatures of dull and lumpish nature and had no more language than beasts. But Sauron had made use of them, teaching them what little they could learn, and increasing their wits with wickedness. Trolls therefore took such language as they could master from the Orcs; and in the Westlands the Stone-trolls spoke a debased form of the Common Speech.
But at the end of the Third Age a troll-race not before seen appeared in southern Mirkwood and in the mountain borders of Mordor. Olog-hai they were called in the Black Speech. That Sauron bred them none doubted, though from what stock was not known. Some held that they were not Trolls but giant Orcs; but the Olog-hai were in fashion of body and mind quite unlike even the largest of Orc-kind, whom they far surpassed in size and power. Trolls they were, but filled with the evil will of their master: a fell race, strong, agile, fierce and cunning, but harder than stone. Unlike the older race of the Twilight they could endure the Sun, so long as the will of Sauron held sway over them. They spoke little, and the only tongue that they knew was the Black Speech of Barad-dûr."
