How did Glamdring, Orcrist and Sting end up in a troll hole?
either men hid them (and they ended up plundered) or else the witch king of Agmar got it when he controlled Eriador, and the trolls got it from that land after it fell.
and a related question: how did the Great Goblin recognize the swords?
Maybe they read the runes...or did orcs spend their evenings around a fire drinking beer and telling stories of the good old days?
Where did they get the names for the Hunger games?
add these things to percy Jackson, and you realize that teen fiction is re introducing them to the legends of the ancient world.