Trolls are slow in the uptake, and mighty suspicious about anything new to them.
Trolls, it is said, were bred by Melkor because he desired a race as powerful as the giant Ents , the Tree-herds.
The folk belief … is that lightning seeks out Trolls and giants, perhaps a reflection the giant-slaying of Thor in Old Norse mythology. Many informants have told collectors that the reason the giants or Trolls are no longer populous is the accuracy and efficiency of the lightning strokes.
They were Trolls. Obviously Trolls. Even Bilbo, in spite of his sheltered life, could see that: from the great heavy faces of them, and their size, and the shape of their legs, not to mention their language, which was not drawing-room fashion at all, at all.
Trolls simply detest the very sight of dwarves (uncooked).
Trolls do not build.
Trolls are only counterfeits, made by the Enemy in the Great Darkness, in mockery of Ents, as Orcs were of Elves.