The big thing is "how did the swords ever get out of Gondolin", because in most versions, Turgon is doing at least some fighting, assumably with Glamdring, during the Fall of Gondolin. Perhaps he didn't, and used the sword in Nírnaeth Arnoediad instead, and one of the exiles took the sword out of Gondolin. Anyway, the swords somehow found its way out of Gondolin, most likely to the Mouths of Sirion. From there, I can see two paths: With Elros or with Elrond.
From their other ancestry we know that Aranrûth (sword of Elu Thingol) belongs to the King of Númenor during the Second Age. Perhaps Turgon's weapons were heirlooms of some noble house of Númenor, and therefore, by extension, of the Dúnedain. In this case, of the northern variety. The previous owner lost the sword in the Trollshaws and it ended up in the troll hoard.
Or then it was Elrond's heirloom, and was used (and lost) in some battle (not necessarily by Elrond himself) and then ended up in the troll hoard. For example Elu Thingol giving Anglachel sets a precedent of an elf-lord giving a mighty weapon for a servant. (And that event didn't go too well, either.)