No matter if those words have an etymology. When I will use them the players will probably ask about their meaning. Problem solved.
To much work to research those etymologies and find good translation options.
I wouldn't link the chavaliers of chapter 3 with Orcus.
Another possible link with Orcus: the NPC with the party is a dustman (he will not reveal his/her faction) faithful of Orcus, and wishes to follow the march in order to protect it and, in the end, report to his cabal about what has been discovered.
But another problem arises. Probably PCs will never uncover the truth about this NPC. He will die (if I am not wrong) in chapter 5. But this problem could be solved later on (maybe even in Dead gods), when the party find him as an undead in service of Tenebrous (I didn't read Dead Gods yet, so I don't know if there is room to arrange something like that).
To much work to research those etymologies and find good translation options.
I wouldn't link the chavaliers of chapter 3 with Orcus.
Another possible link with Orcus: the NPC with the party is a dustman (he will not reveal his/her faction) faithful of Orcus, and wishes to follow the march in order to protect it and, in the end, report to his cabal about what has been discovered.
But another problem arises. Probably PCs will never uncover the truth about this NPC. He will die (if I am not wrong) in chapter 5. But this problem could be solved later on (maybe even in Dead gods), when the party find him as an undead in service of Tenebrous (I didn't read Dead Gods yet, so I don't know if there is room to arrange something like that).