Probably from the latin arcus, meaning "arch" or "bow." I don't think it has a specific intended meaning in this case, but is more used to imply a technological/archaic/arcane connection; that is, this person is not only a flagellant, but they are a mechanized super-flagellant.
That said, this is all idle theorizing, not based in fact.
CSM Plog,
Tactica
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!
