I think tolken may have put a tradition of knights in lotr with that necklace aragorn has from arwen.In the middle ages befor a joust if a women was in love with a knight she would give him a posetion of hers ushaly a pice of cloth of hers and if he loved her back he would wear it during a joust and I think that is why aragorn wears the necklace
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You will be in awe of my knowlage of the Middle Ages!