De onde vem o tesouro da caverna dos trolls?

O tesouro na caverna dos Trolls foi reunido ao longo do tempo, atraindo viajantes e pilhando aldeias e fazendas. Sempre famintos e sempre gananciosos, os Trolls colecionavam tudo o que consideravam de valor de suas vítimas e acumulavam-no na caverna em que estavam escondidos durante o dia. Pode-se supor que os trolls tinham outras cavernas que eles usaram ao longo de seu caminho para baixo das montanhas e teriam trazido seu tesouro acumulado com eles quando se mudaram ...

Em relação ao Glamdring e Orcrist, De acordo com LOTR Wikia Armas élficas da Primeira Era foram consideradas espólios de guerra e mais tarde usado por Anões contra Orcs na Batalha de Nanduhirion

Years after the battle, the dwarven wielders of the Elvish swords were most likely relocating to Lindon during the Fell Winter of 2911 when they were waylaid unsuspectingly by trolls in the Ettenmoors. Thus the swords ultimately fell into the hands of the three trolls from The Hobbit by the end of the Third Age.

Isso é parcialmente respondido no próprio livro, em primeiro lugar na descrição inicial do covil do troll:

There were bones on the floor and a nasty smell was in the air; but there was a good deal of food jumbled carelessly on shelves and on the ground, among an untidy litter of plunder, of all sorts from brass buttons to pots full of gold coins standing in a corner. There were lots of clothes, too, hanging on the walls-too small for trolls, I am afraid they belonged to victims - and among them were several swords of various makes, shapes, and sizes. Two caught their eyes particularly, because of their beautiful scabbards and jewelled hilts.

E em segundo lugar, quando Elrond examina as espadas:

That day he looked at the swords they had brought from the trolls' lair, and he said: "These are not troll-make. They are old swords, very old swords of the High Elves of the West, my kin. They were made in Gondolin for the Goblin-wars. They must have come from a dragon's hoard or goblin plunder, for dragons and goblins destroyed that city many ages ago."

"I could not say,"said Elrond, "but one may guess that your trolls had plundered other plunderers or come on the remnants of old robberies in some hold in the mountains. I have heard that there are still forgotten treasures of old to be found in the deserted caverns of the mines of Moria, since the dwarf and goblin war."

Isso é tudo o que é dito sobre o assunto.